### Go: QuantityContext Initialization and Methods

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Defines the QuantityContext structure and associated functions for creating new contexts and accepting visitors. It also includes methods for retrieving the parser, the rule context, checking the context type, accessing a number terminal, and converting the context to a string tree. The Unit method specifically retrieves an IUnitContext.

```go
type QuantityContext struct {
	antlr.BaseParserRuleContext
	// contains filtered or unexported fields
}

```

```go
func NewEmptyQuantityContext() *QuantityContext

```

```go
func NewQuantityContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *QuantityContext

```

```go
func (s *QuantityContext) Accept(visitor antlr.ParseTreeVisitor) interface{}

```

```go
func (s *QuantityContext) GetParser() antlr.Parser

```

```go
func (s *QuantityContext) GetRuleContext() antlr.RuleContext

```

```go
func (*QuantityContext) IsQuantityContext()

```

```go
func (s *QuantityContext) NUMBER() antlr.TerminalNode

```

```go
func (s *QuantityContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string

```

```go
func (s *QuantityContext) Unit() IUnitContext

```

--------------------------------

### Get Time unit symbol in Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/units

The Symbol method, when called on a Time object, returns the string representation (symbol) of that time unit. For example, it might return "s" for Seconds.

```go
func (t Time) Symbol() string
```

--------------------------------

### Get URI String from ContainedResource (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.4.0/internal/containedresource

Provides the Uniform Resource Identifier (URI) of a contained resource as a simple string. The URI is formatted as 'Type/ID', for example, 'Patient/123'. This is a convenient string representation for URIs.

```Go
func URIString(cr *bcrpb.ContainedResource) string {
	// ... implementation ...
}
```

--------------------------------

### Go: ProgContext Methods

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Includes standard ANTLR methods like Accept, GetRuleContext, and GetParser, along with specific methods like EOF, Expression, IsProgContext, and ToStringTree for the ProgContext.

```go
func (s *ProgContext) Accept(visitor antlr.ParseTreeVisitor) interface{} {
  // ... implementation details ...
}
func (s *ProgContext) EOF() antlr.TerminalNode {
  // ... implementation details ...
}
func (s *ProgContext) Expression() IExpressionContext {
  // ... implementation details ...
}
func (s *ProgContext) GetParser() antlr.Parser {
  // ... implementation details ...
}
func (s *ProgContext) GetRuleContext() antlr.RuleContext {
  // ... implementation details ...
}
func (*ProgContext) IsProgContext() {
  // ... implementation details ...
}
func (s *ProgContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string {
  // ... implementation details ...
}
```

--------------------------------

### Get URI from ContainedResource (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.4.0/internal/containedresource

Retrieves the Uniform Resource Identifier (URI) of a contained resource in the format of a FHIR URI object. The URI is constructed as 'Type/ID', for example, 'Patient/123'. This function is useful for generating references to contained resources.

```Go
func URI(cr *bcrpb.ContainedResource) *dtpb.Uri {
	// ... implementation ...
}
```

--------------------------------

### Compile Option: Enable Experimental Functions

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.2.1/fhirpath/compopts_tab=versions

The `WithExperimentalFuncs` function returns a `CompileOption` that enables experimental functions within the FHIRPath engine. Use this option with caution as experimental features may change or be removed in future versions.

```Go
func WithExperimentalFuncs() opts.CompileOption
```

--------------------------------

### Create FHIR Bundle GET Entry (Versioned Read Interaction)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.1.0/internal/bundle

Constructs a bundle entry for a GET request to retrieve a specific versioned FHIR resource, corresponding to the FHIR 'vread' interaction. Supports batch or transaction bundles. If version is empty, it performs a simple GET.

```go
func NewVersionedGetEntry(typeName resource.Type, id string, version string, opts ...EntryOption) *bcrpb.Bundle_Entry {
	// ... implementation details ...
}
```

--------------------------------

### Bundle Entry Option Configuration (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/bundle_tab=versions

Defines `EntryOption` interface and associated functions to configure specific options for individual bundle entries. This includes setting the `If-Match` header using `SetEntryIfMatch`, specifying the `Content-Type` via `WithFullURL`, and conditionally adding entries with `WithIfNoneExist`. `WithGeneratedFullURL` can be used for auto-generating URLs.

```go
+ type EntryOption interface
+ func WithFullURL(url string) EntryOption
+ func WithGeneratedFullURL() EntryOption
+ func WithIfNoneExist(identifier *dtpb.Identifier) EntryOption
+ func SetEntryIfMatch(entry *bcrpb.Bundle_Entry)
```

--------------------------------

### Quantity Comparison and Utility Functions (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/system

Provides methods for comparing Quantity objects, negating their values, and converting them to string or Protocol Buffer formats. Includes equality checks and less-than comparisons, with error handling for mismatched units or types.

```Go
func (q Quantity) Equal(q2 Quantity) bool
func (q Quantity) Less(input Any) (Boolean, error)
func (q Quantity) Name() string
func (q Quantity) Negate() Quantity
func (q Quantity) String() string
func (q Quantity) ToProtoQuantity() *dtpb.Quantity
func (q Quantity) TryEqual(input Any) (bool, bool)
```

--------------------------------

### Create FHIR Bundle Entry for Getting Versioned Resource (VRead Interaction)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/bundle

Constructs a FHIR bundle entry for a GET request to retrieve a specific version of a resource (FHIR 'vread' interaction). Suitable for batch/transaction bundles. If the version is empty, it defaults to a simple GET (head version). It does not support history interactions.

```go
func NewVersionedGetEntry(typeName resource.Type, id string, version string, opts ...EntryOption) *bcrpb.Bundle_Entry {
  // ... implementation details ...
}
```

--------------------------------

### Go: ImpliesExpressionContext Structure and Methods

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Defines the ImpliesExpressionContext struct, embedding ExpressionContext. It includes a constructor NewImpliesExpressionContext and methods like Accept, AllExpression to get all child expressions, Expression to get a specific child expression, and GetRuleContext.

```go
type ImpliesExpressionContext struct {
	ExpressionContext
}

func NewImpliesExpressionContext(parser antlr.Parser, ctx antlr.ParserRuleContext) *ImpliesExpressionContext {
	return &ImpliesExpressionContext{}
}

func (s *ImpliesExpressionContext) Accept(visitor antlr.ParseTreeVisitor) interface{} {
	return nil
}

func (s *ImpliesExpressionContext) AllExpression() []IExpressionContext {
	return nil
}

func (s *ImpliesExpressionContext) Expression(i int) IExpressionContext {
	return nil
}

func (s *ImpliesExpressionContext) GetRuleContext() antlr.RuleContext {
	return nil
}
```

--------------------------------

### Create Test QuestionnaireResponse Resource

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.3.0/internal/fhirtest

Generates a test QuestionnaireResponse resource with predefined fields like subject and status. It accepts optional resource options for further customization. Dependencies include the testing package and qrpb.QuestionnaireResponse.

```go
func NewQuestionnaireResponse(t *testing.T, opts ...ResourceOption) *qrpb.QuestionnaireResponse
```

--------------------------------

### Create Test QuestionnaireResponse Resource (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/internal/fhirtest

Generates a test QuestionnaireResponse resource with pre-populated subject and status fields. It accepts optional ResourceOptions for further customization. Errors during test setup will cause the test to fail.

```Go
func NewQuestionnaireResponse(t *testing.T, opts ...ResourceOption) *qrpb.QuestionnaireResponse {
  // ... implementation details ...
}
```

--------------------------------

### Create FHIR Bundle GET Entry (Read Interaction)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.1.0/internal/bundle

Constructs a bundle entry for a GET request to retrieve the head version of a FHIR resource, corresponding to the FHIR 'read' interaction. It is designed for batch or transaction bundles.

```go
func NewGetEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry {
	// ... implementation details ...
}
```

--------------------------------

### TypeSpecifierContext Methods in fhirpath_parser.go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.1.0/fhirpath/internal/grammar

Details various methods available for the TypeSpecifierContext in fhirpath_parser.go. These include accepting visitors, getting the parser, retrieving the RuleContext, checking if it's a TypeSpecifierContext, getting a QualifiedIdentifier, and converting to a string representation of the rule tree.

```go
func (s *TypeSpecifierContext) Accept(visitor antlr.ParseTreeVisitor) interface{} {
    // Implementation details would be here
    panic("implement me")
}

func (s *TypeSpecifierContext) GetParser() antlr.Parser {
    // Implementation details would be here
    panic("implement me")
}

func (s *TypeSpecifierContext) GetRuleContext() antlr.RuleContext {
    return s
}

func (*TypeSpecifierContext) IsTypeSpecifierContext() {
    // Method body
}

func (s *TypeSpecifierContext) QualifiedIdentifier() IQualifiedIdentifierContext {
    // Implementation details would be here
    panic("implement me")
}

func (s *TypeSpecifierContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string {
    // Implementation details would be here
    panic("implement me")
}
```

--------------------------------

### Go: TermContext Initialization and Methods

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Details the TermContext structure and its associated initialization functions. It includes methods for copying context data, retrieving the parser and rule context, checking if it's a TermContext, and converting it to a string representation of the parse tree. These are standard ANTLR context operations.

```go
type TermContext struct {
	antlr.BaseParserRuleContext
	// contains filtered or unexported fields
}

```

```go
func NewEmptyTermContext() *TermContext

```

```go
func NewTermContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *TermContext

```

```go
func (s *TermContext) CopyAll(ctx *TermContext)

```

```go
func (s *TermContext) GetParser() antlr.Parser

```

```go
func (s *TermContext) GetRuleContext() antlr.RuleContext

```

```go
func (*TermContext) IsTermContext()

```

```go
func (s *TermContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string

```

--------------------------------

### Apply Function

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.3.0/internal/bundleopt

Applies a set of bundle options to construct a bundle from raw data.

```APIDOC
## func Apply

### Description
Applies a set of bundle options to construct a bundle from raw data.

### Method
N/A (Function Signature)

### Endpoint
N/A (Package Function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```go
func Apply(bundle *bcrpb.Bundle, opts ...BundleOption)
```

### Response
#### Success Response (200)
N/A (Function returns void, modifies bundle in place)

#### Response Example
N/A
```

--------------------------------

### Create FHIR Bundle Entry Functions (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.1.0/internal/bundle_tab=versions

Offers functions to create specific types of FHIR Bundle entries, such as entries for creating new resources, updating resources (PUT), deleting resources, performing GET requests, and versioned GET requests. Entry options can be applied.

```Go
func NewCollectionEntry(res fhir.Resource) *bcrpb.Bundle_Entry
func NewDeleteEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry
func NewGetEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry
func NewPostEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry
func NewPutEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry
func NewVersionedGetEntry(typeName resource.Type, id string, version string, opts ...EntryOption) *bcrpb.Bundle_Entry
```

--------------------------------

### Create a Simple Resolver - Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.3.0/fhirpath/resolver/resolvertest_tab=versions

Creates a simple resolver for testing purposes. It takes optional configuration options to customize its behavior. This is useful for mocking dependencies in tests.

```go
func NewSimpleResolver(opts ...SimpleResolverOption) resolver.Resolver

type SimpleResolverOption interface

func Entry(key string, resources ...fhirpath.Resource) SimpleResolverOption
```

--------------------------------

### Create FHIR Bundle Entry

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/bundle

Functions for creating individual FHIR Bundle Entries. This includes creating entries for collections, GET requests, POST requests, PUT requests, DELETE requests, and versioned GET requests. These functions take resource details or FHIR resources as input.

```go
func NewCollectionEntry(res fhir.Resource) *bcrpb.Bundle_Entry
```

```go
func NewGetEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry
```

```go
func NewPostEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry
```

```go
func NewPutEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry
```

```go
func NewDeleteEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry
```

```go
func NewVersionedGetEntry(typeName resource.Type, id string, version string, opts ...EntryOption) *bcrpb.Bundle_Entry
```

--------------------------------

### UnitContext Constructor and Methods in Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Provides constructors for UnitContext and its associated methods for ANTLR parsing. Includes visitor acceptance (Accept), rule context retrieval (GetRuleContext), parser access (GetParser), and specific getters for DateTimePrecision, PluralDateTimePrecision, and STRING terminal.

```Go
type UnitContext struct {
	antlr.BaseParserRuleContext
	// contains filtered or unexported fields
}

func NewEmptyUnitContext() *UnitContext
func NewUnitContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *UnitContext
func (s *UnitContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *UnitContext) DateTimePrecision() IDateTimePrecisionContext
func (s *UnitContext) GetParser() antlr.Parser
func (s *UnitContext) GetRuleContext() antlr.RuleContext
func (s *UnitContext) IsUnitContext() 
func (s *UnitContext) PluralDateTimePrecision() IPluralDateTimePrecisionContext
func (s *UnitContext) STRING() antlr.TerminalNode
func (s *UnitContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string
```

--------------------------------

### Go: Create FHIR Bundle Entries

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.1.0/internal/bundle

Includes functions for creating specific types of FHIR Bundle Entries, such as collection entries, delete entries, get entries, post entries, put entries, and versioned get entries. These functions facilitate the creation of individual entries within a bundle.

```Go
func NewCollectionEntry(res fhir.Resource) *bcrpb.Bundle_Entry

NewCollectionEntry takes in a FHIR Resource and creates a BundleEntry for the resource.
```

```Go
func NewDeleteEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry

NewDeleteEntry creates a Bundle Entry for a delete operation.
```

```Go
func NewGetEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry

NewGetEntry creates a Bundle Entry for a get operation.
```

```Go
func NewPostEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry

NewPostEntry creates a Bundle Entry for a post operation.
```

```Go
func NewPutEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry

NewPutEntry creates a Bundle Entry for a put operation.
```

```Go
func NewVersionedGetEntry(typeName resource.Type, id string, version string, opts ...EntryOption) *bcrpb.Bundle_Entry

NewVersionedGetEntry creates a Bundle Entry for a versioned get operation.
```

--------------------------------

### Get Function Context in Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Retrieves the IFunctionContext from a FunctionInvocationContext. This is a method on the FunctionInvocationContext struct.

```go
func (s *FunctionInvocationContext) Function() IFunctionContext {
	// Implementation details omitted for brevity
}
```

--------------------------------

### Go: Context Initialization and Cloning Functions

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/expr%40v1.3_tab=versions

Includes functions for managing the `Context` in Go. `InitializeContext` creates a new context from an input collection, while `Clone` provides a way to duplicate an existing context. These are essential for maintaining state during expression evaluation.

```go
type Context struct
	BeforeLastResult system.Collection
	ExternalConstants map[string]any
	LastResult system.Collection
	Now time.Time
	func InitializeContext(input system.Collection) *Context
	func (c *Context) Clone() *Context
```

--------------------------------

### ApplyOptions Function

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.2.1/fhirpath/internal/opts

ApplyOptions applies all the options to the given configuration.

```APIDOC
## ApplyOptions

### Description
ApplyOptions applies all the options to the given configuration.

### Method
`func`

### Endpoint
N/A (Function)

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
None

### Response
#### Success Response
- `*T` (pointer to generic type) - The configuration with options applied.
- `error` - An error if any option fails to apply.

#### Response Example
```json
{
  "result": "<pointer to updated configuration>",
  "error": "null or error message"
}
```
```

--------------------------------

### Substring Function

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.3.0/fhirpath/internal/funcs/impl

Extracts a portion of a string based on start position and optional length.

```APIDOC
## Substring

### Description
Extracts a portion of the input string starting from a specified zero-based position. An optional length parameter limits the number of characters returned.

### Method
N/A (Function within a library)

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
- **input** (system.Collection) - A collection containing the string from which to extract a substring.
- **args** (expr.Expression) - The first expression should be an integer representing the zero-based start position. The second optional expression should be an integer representing the maximum number of characters to return.

### Request Example
```json
{
  "input": ["Programming"],
  "args": [3, 4]
}
```

### Response
#### Success Response (200)
- **result** (system.Collection) - A collection containing the extracted substring.

#### Response Example
```json
{
  "result": ["gram"]
}
```
```

--------------------------------

### Create FHIR Bundle Entry for Getting Resource (Read Interaction)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/bundle

Constructs a FHIR bundle entry for a GET request to retrieve the head version of a resource (FHIR 'read' interaction). It is designed for batch or transaction bundles. Avoid crafting special IDs for versioned resources; use VersionedGetEntry instead.

```go
func NewGetEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry {
  // ... implementation details ...
}
```

--------------------------------

### Go: Parameter List Context Creation and Methods

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.5.0/fhirpath/internal/grammar

Provides functionality for handling parameter lists in FHIRPath expressions. Includes constructors for empty and standard parameter lists, methods for visitor acceptance, expression access, and context retrieval. Uses antlr.

```Go
type ParamListContext struct {
	antlr.BaseParserRuleContext
	// contains filtered or unexported fields
}

func NewEmptyParamListContext() *ParamListContext {
	// Implementation details would be here
}

func NewParamListContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *ParamListContext {
	// Implementation details would be here
}

func (s *ParamListContext) Accept(visitor antlr.ParseTreeVisitor) interface{} {
	// Implementation details would be here
}

func (s *ParamListContext) AllExpression() []IExpressionContext {
	// Implementation details would be here
}

func (s *ParamListContext) Expression(i int) IExpressionContext {
	// Implementation details would be here
}

func (s *ParamListContext) GetParser() antlr.Parser {
	// Implementation details would be here
}

func (s *ParamListContext) GetRuleContext() antlr.RuleContext {
	// Implementation details would be here
}

func (*ParamListContext) IsParamListContext() {
	// Implementation details would be here
}

func (s *ParamListContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string {
	// Implementation details would be here
}
```

--------------------------------

### Get Identifier List from FHIR Resource

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/internal/resource

Retrieves a list of FHIR Identifiers from a given FHIR Resource. It uses duck typing to check if the resource implements methods for getting single or multiple identifiers. Returns an error if the resource does not implement the GetIdentifier() method. Handles cases where identifiers might be missing.

```go
func GetIdentifierList(res fhir.Resource) ([]*dtpb.Identifier, error) {
	return nil, nil
}
```

--------------------------------

### UnitContext Constructors and Methods (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.5.0/fhirpath/internal/grammar

Provides documentation for the UnitContext in Go, including constructors and methods such as Accept, DateTimePrecision, GetParser, GetRuleContext, IsUnitContext, PluralDateTimePrecision, STRING, and ToStringTree. This context is used for parsing units in FHIRPath.

```Go
type UnitContext struct {
	antlr.BaseParserRuleContext
	// contains filtered or unexported fields
}
func NewEmptyUnitContext() *UnitContext
func NewUnitContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *UnitContext
func (s *UnitContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *UnitContext) DateTimePrecision() IDateTimePrecisionContext
func (s *UnitContext) GetParser() antlr.Parser
func (s *UnitContext) GetRuleContext() antlr.RuleContext
func (s *UnitContext) IsUnitContext()
func (s *UnitContext) PluralDateTimePrecision() IPluralDateTimePrecisionContext
func (s *UnitContext) STRING() antlr.TerminalNode
func (s *UnitContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string
```

--------------------------------

### Get Status Code From Entry

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.4.0/internal/bundle

Returns the numeric http code from Bundle_Entry.response.status.

```APIDOC
## Get Status Code From Entry

### Description
Returns the numeric http code from Bundle_Entry.response.status. Added in v1.2.1.

### Method
N/A (Function call)

### Endpoint
N/A

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
- **entry** (*bcrpb.Bundle_Entry) - The bundle entry to process.

### Request Example
```go
statusCode, err := StatusCodeFromEntry(entry)
```

### Response
#### Success Response (200)
- **int** - The numeric HTTP status code.
- **error** - An error if the status code cannot be determined.

#### Response Example
```json
{
  "int": 200,
  "error": null
}
```
```

--------------------------------

### Apply Function

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/bundleopt

The Apply function applies a series of bundle options to a given bundle.

```APIDOC
## Apply

### Description
Applies a series of bundle options to a given bundle.

### Method
func

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (200)
N/A

#### Response Example
N/A
```

--------------------------------

### Go: Get Identity ID

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.5.0/internal/resource

Returns the ID part of the Identity object.

```Go
func (i *Identity) ID() string
{
    // Implementation for ID() method
}
```

--------------------------------

### StartsWith Function

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/fhirpath/internal/funcs/impl

Checks if an input string begins with a specified prefix. Returns a boolean value indicating the result.

```APIDOC
## StartsWith

### Description
Returns true if the input string starts with the given prefix.

### Method
N/A (Function within a library)

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (200)
N/A

#### Response Example
N/A
```

--------------------------------

### Take Function

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.3.0/fhirpath/internal/funcs/impl

Returns the first 'n' items from a collection.

```APIDOC
## Take

### Description
Returns a new collection containing the first 'num' items from the input collection, or fewer if the collection has less than 'num' items. If 'num' is less than or equal to zero, or if the input collection is empty, an empty collection is returned.

### Method
N/A (Function within a library)

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
- **input** (system.Collection) - The input collection from which to take items.
- **args** (expr.Expression) - The first expression should be an integer representing the number of items to take.

### Request Example
```json
{
  "input": [1, 2, 3, 4, 5],
  "args": [3]
}
```

### Response
#### Success Response (200)
- **result** (system.Collection) - A collection containing the first specified number of items.

#### Response Example
```json
{
  "result": [1, 2, 3]
}
```

### FHIRPath Documentation
[https://hl7.org/fhirpath/N1/#takenum-integer-collection](https://hl7.org/fhirpath/N1/#takenum-integer-collection)
```

--------------------------------

### Get Parser for DateTime Precision Context in Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.2.1/fhirpath/internal/grammar

Retrieves the antlr.Parser associated with the DateTimePrecisionContext.

```Go
func (s *DateTimePrecisionContext) GetParser() antlr.Parser
```

--------------------------------

### ProgContext Structure and Methods (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Details the ProgContext, inheriting from antlr.BaseParserRuleContext. This context represents a program structure and includes methods for creation, visitor acceptance, and retrieving the parser, rule context, and EOF terminal. It also contains a method to verify if it is a ProgContext and to generate a string representation of its parse tree.

```Go
type ProgContext struct {
	antlr.BaseParserRuleContext
	// contains filtered or unexported fields
}

func NewEmptyProgContext() *ProgContext

func NewProgContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *ProgContext

func (s *ProgContext) Accept(visitor antlr.ParseTreeVisitor) interface{}

func (s *ProgContext) EOF() antlr.TerminalNode

func (s *ProgContext) Expression() IExpressionContext

func (s *ProgContext) GetParser() antlr.Parser

func (s *ProgContext) GetRuleContext() antlr.RuleContext

func (*ProgContext) IsProgContext()

func (s *ProgContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string
```

--------------------------------

### Time Utility Functions

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.3.0/fhirpath/system

Utility functions for Time objects, such as getting the type name and string representation.

```APIDOC
## Name

### Description
Name returns the type name.

### Method
N/A (This is a method on the Time object, not a standalone endpoint)

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (200)
- **string** (string) - The name of the type.

#### Response Example
N/A

## String

### Description
String formats the time as a time string.

### Method
N/A (This is a method on the Time object, not a standalone endpoint)

### Endpoint
N/A

### Parameters
#### Path Parameters
N/A

#### Query Parameters
N/A

#### Request Body
N/A

### Request Example
N/A

### Response
#### Success Response (200)
- **string** (string) - The formatted time string.

#### Response Example
N/A
```

--------------------------------

### Accept Visitor Pattern Implementation in Go (ANTLR)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.3.0/fhirpath/internal/grammar

Demonstrates the implementation of the Accept method for various ANTLR-generated context types in Go. This method is crucial for the visitor design pattern, allowing traversal and processing of the parse tree.

```go
func (s *TimeLiteralContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *TotalInvocationContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *TypeExpressionContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *TypeSpecifierContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *UnionExpressionContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *UnitContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
```

--------------------------------

### Bundle Entry Creation Functions (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/bundle_tab=versions

Provides functions to create different types of FHIR Bundle entries, such as POST, PUT, DELETE, GET, and versioned GET entries. These functions utilize `EntryOption` to configure entry-specific details like conditional URLs or match headers. Dependencies include `resource.Type`, `EntryOption`, and potentially `fhir.Resource` for entry content.

```go
func NewPostEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry
+ func NewPutEntry(res fhir.Resource, opts ...EntryOption) *bcrpb.Bundle_Entry
+ func NewDeleteEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry
+ func NewGetEntry(typeName resource.Type, id string, opts ...EntryOption) *bcrpb.Bundle_Entry
+ func NewVersionedGetEntry(typeName resource.Type, id string, version string, opts ...EntryOption) *bcrpb.Bundle_Entry
```

--------------------------------

### Get Resource ID from Identity (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.5.0/internal/resource

Retrieves the resource ID from an Identity object.

```go
func (i *Identity) ID() string {
	// ... implementation details ...
}
```

--------------------------------

### NewProgContext Constructor

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/fhirpath/internal/grammar

Constructs a new ProgContext with a given parser, parent rule context, and invoking state. This is the standard way to create a ProgContext during parsing.

```go
func NewProgContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *ProgContext

```

--------------------------------

### Date and Trace Functions

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.5.0/fhirpath/internal/funcs/impl

Functions for getting the current date and custom diagnostic logging.

```APIDOC
## Today

### Description
Returns the current date as a system.Date object.

### Method
Not Applicable (Function)

### Endpoint
Not Applicable

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "message": "Get today's date"
}
```

### Response
#### Success Response (200)
- **output** (Date) - The current date.

#### Response Example
```json
{
  "output": "2023-10-27"
}
```

## Trace

### Description
Implements the FHIRPath "trace" function for custom diagnostic logging during evaluation.

### Method
Not Applicable (Function)

### Endpoint
Not Applicable

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```json
{
  "expression": "Patient.name",
  "logName": "patientNameTrace"
}
```

### Response
#### Success Response (200)
- **output** (Collection) - The result of the evaluated expression.

#### Response Example
```json
{
  "output": [
    {
      "text": "John Doe"
    }
  ]
}
```
```

--------------------------------

### Create Identity with New Version

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/resource

Returns a new Identity object with the specified VersionID.

```go
func (i *Identity) WithNewVersion(versionID string) *Identity
```

--------------------------------

### ParamListContext Constructors and Methods (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/fhirpath/internal/grammar

Defines constructors for creating ParamListContext objects, both empty and with specified parser and parent rule context. Includes methods to accept visitors and retrieve all or specific Expression child contexts.

```go
func NewEmptyParamListContext() *ParamListContext
func NewParamListContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *ParamListContext
func (s *ParamListContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *ParamListContext) AllExpression() []IExpressionContext
func (s *ParamListContext) Expression(i int) IExpressionContext
```

--------------------------------

### Get Rule Context for DateTime Precision Context in Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.2.1/fhirpath/internal/grammar

Retrieves the underlying antlr.RuleContext for a DateTimePrecisionContext.

```Go
func (s *DateTimePrecisionContext) GetRuleContext() antlr.RuleContext
```

--------------------------------

### FHIRPath Context Management (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.2.1/fhirpath/internal/expr_tab=versions

Demonstrates the creation and manipulation of the Context object in the fhirpath-go library. This includes initializing a new context, cloning an existing one, and accessing context-specific values.

```Go
type Context
	BeforeLastResult system.Collection
	ExternalConstants map[string]any
	LastResult system.Collection
	Now time.Time
	func InitializeContext(input system.Collection) *Context
	func (c *Context) Clone() *Context
	func (c *Context) Deadline() (deadline time.Time, ok bool)
	func (c *Context) Done() <-chan struct{}
	func (c *Context) Err() error
	func (c *Context) Value(key any) any
```

--------------------------------

### Get FHIR Resource ID from Identity

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/resource

Returns the resource ID from an Identity object.

```go
func (i *Identity) ID() string
```

--------------------------------

### QuantityContext Methods and Constructors (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.4.0/fhirpath/internal/grammar

Defines constructors and methods for the QuantityContext, including creating empty or new contexts, accepting visitors, retrieving the parser and rule context, checking if it's a QuantityContext, accessing NUMBER terminals, converting to a string tree, and getting the Unit. These are generated by ANTLR.

```Go
func NewEmptyQuantityContext() *QuantityContext

```

```Go
func NewQuantityContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *QuantityContext

```

```Go
func (s *QuantityContext) Accept(visitor antlr.ParseTreeVisitor) interface{}

```

```Go
func (s *QuantityContext) GetParser() antlr.Parser

```

```Go
func (s *QuantityContext) GetRuleContext() antlr.RuleContext

```

```Go
func (*QuantityContext) IsQuantityContext()

```

```Go
func (s *QuantityContext) NUMBER() antlr.TerminalNode

```

```Go
func (s *QuantityContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string

```

```Go
func (s *QuantityContext) Unit() IUnitContext

```

--------------------------------

### Get URI of ContainedResource as string (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/containedresource

Returns the URI of a contained resource as a string. The format is Type/ID.

```Go
func URIString(cr *bcrpb.ContainedResource) string {
	// ... implementation ...
}

// Example Usage:
// resourceURIString := URIString(containedResource)

```

--------------------------------

### Go: PluralDateTimePrecisionContext Methods

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Includes standard ANTLR methods like Accept and GetRuleContext, along with specific methods like GetParser, IsPluralDateTimePrecisionContext, and ToStringTree for the PluralDateTimePrecisionContext.

```go
func (s *PluralDateTimePrecisionContext) Accept(visitor antlr.ParseTreeVisitor) interface{} {
  // ... implementation details ...
}
func (s *PluralDateTimePrecisionContext) GetParser() antlr.Parser {
  // ... implementation details ...
}
func (s *PluralDateTimePrecisionContext) GetRuleContext() antlr.RuleContext {
  // ... implementation details ...
}
func (*PluralDateTimePrecisionContext) IsPluralDateTimePrecisionContext() {
  // ... implementation details ...
}
func (s *PluralDateTimePrecisionContext) ToStringTree(ruleNames []string, recog antlr.Recognizer) string {
  // ... implementation details ...
}
```

--------------------------------

### Create FHIR Bundle Transactions and Entries in Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.4.0/internal/bundle_tab=versions

This Go code snippet demonstrates how to create different types of FHIR Bundles, such as transaction, batch, collection, and searchset, using the Verily FHIRPath Go module. It also shows how to create individual bundle entries, including delete, get, post, put, and versioned get entries, with various configuration options.

```go
import (
	"errors"
	"fmt"
	"time"

	"github.com/Verily-src/fhir-go/fhir"
	"github.com/Verily-src/fhir-go/fhir/bundle"
	"github.com/Verily-src/fhir-go/fhir/bundle/bundleopt"
	cpb "github.com/Verily-src/fhir-go/fhir/proto/coding/codes"
	dtpb "github.com/Verily-src/fhir-go/fhir/proto/datatypes"
	"github.com/Verily-src/fhir-go/fhir/proto/resource"
	bcrpb "github.com/Verily-src/fhir-go/fhir/proto/resource/bundle"
)

// Example usage of functions to create FHIR Bundles and Entries

// Create a new transaction bundle
transactionBundle := bundle.NewTransaction(bundle.WithEntries(
	bundle.NewPostEntry(fhir.Resource{Type: "Patient", ID: "123"}),
	bundle.NewPutEntry(fhir.Resource{Type: "Observation", ID: "456"}),
))

// Create a new batch bundle
batchBundle := bundle.NewBatch()

// Create a new collection bundle
collectionBundle := bundle.NewCollection()

// Create a new searchset bundle
searchsetBundle := bundle.NewSearchset()

// Create a new transaction response bundle
transactionResponse := bundle.NewTransactionResponse()

// Create a new delete entry
deleteEntry := bundle.NewDeleteEntry("Patient", "789")

// Create a new get entry
getEntry := bundle.NewGetEntry("Observation", "1011")

// Create a new post entry with options
postEntry := bundle.NewPostEntry(fhir.Resource{Type: "Practitioner", ID: "1213"}, bundle.WithGeneratedFullURL())

// Create a new put entry with options
putEntry := bundle.NewPutEntry(fhir.Resource{Type: "Medication", ID: "1415"}, bundle.WithIfNoneExist(&dtpb.Identifier{}))

// Create a new versioned get entry
versionedGetEntry := bundle.NewVersionedGetEntry("AllergyIntolerance", "1617", "v1")

// Patch an entry from bytes
identity := &resource.Identity{}
payload := []byte("some payload")
patchEntry, err := bundle.PatchEntryFromBytes(identity, payload)
if err != nil {
	// Handle error
}

// Set entry if match
// bundle.SetEntryIfMatch(entry)

// Example of Option interface
options := []bundle.Option{
	bundle.WithEntries(
		bundle.NewCollectionEntry(fhir.Resource{Type: "Encounter", ID: "1819"}),
	),
	bundle.WithTimestampNow(),
}

// Use options to create a bundle
newBundleWithOptions := bundle.New("collection", options...)

```

--------------------------------

### Go: ParamListContext Get RuleContext

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Returns the ANTLR RuleContext for this ParamListContext. This provides access to the underlying ANTLR parsing context.

```go
func (s *ParamListContext) GetRuleContext() antlr.RuleContext
```

--------------------------------

### Create New Identity Version (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/internal/resource%40v1.2

The WithNewVersion function returns a new Identity object with a specified VersionID. It takes a string representing the version ID as input and returns a pointer to an Identity object.

```Go
func (i *Identity) WithNewVersion(versionID string) *Identity {
  // Implementation details omitted for brevity
  return i
}
```

--------------------------------

### Go: OrExpressionContext Get RuleContext

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Returns the ANTLR RuleContext for this OrExpressionContext, providing access to the underlying ANTLR parsing information.

```go
func (s *OrExpressionContext) GetRuleContext() antlr.RuleContext
```

--------------------------------

### ProgContext Constructor and Methods (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/fhirpath/internal/grammar

Defines constructors for ProgContext and methods for accepting visitors, accessing the EOF terminal node and the Expression child context, and retrieving the parser and ANTLR RuleContext.

```go
func NewEmptyProgContext() *ProgContext
func NewProgContext(parser antlr.Parser, parent antlr.ParserRuleContext, invokingState int) *ProgContext
func (s *ProgContext) Accept(visitor antlr.ParseTreeVisitor) interface{}
func (s *ProgContext) EOF() antlr.TerminalNode
func (s *ProgContext) Expression() IExpressionContext
func (s *ProgContext) GetParser() antlr.Parser
func (s *ProgContext) GetRuleContext() antlr.RuleContext
```

--------------------------------

### Go: NumberLiteralContext Get RuleContext

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Returns the ANTLR RuleContext for this NumberLiteralContext, providing access to the underlying ANTLR parsing information.

```go
func (s *NumberLiteralContext) GetRuleContext() antlr.RuleContext
```

--------------------------------

### String StartsWith Function in Go

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/fhirpath/internal/funcs/impl

The StartsWith function checks if an input string begins with a specified prefix. It takes a context, input collection, and a variable number of expressions as arguments. It returns a collection and an error.

```go
func StartsWith(ctx *expr.Context, input system.Collection, args ...expr.Expression) (system.Collection, error)
```

--------------------------------

### Go: NullLiteralContext Get RuleContext

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Returns the ANTLR RuleContext for this NullLiteralContext, providing access to the underlying ANTLR parsing information.

```go
func (s *NullLiteralContext) GetRuleContext() antlr.RuleContext
```

--------------------------------

### Create Test ResearchSubject Resource (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/internal/fhirtest

Generates a test ResearchSubject resource with default values for individual, status ('ELIGIBLE'), and study. Customizations can be provided via ResourceOptions. Test setup errors result in test failure.

```Go
func NewResearchSubject(t *testing.T, opts ...ResourceOption) *rsubpb.ResearchSubject {
  // ... implementation details ...
}
```

--------------------------------

### Go: MultiplicativeExpressionContext Get RuleContext

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath/internal/grammar

Returns the ANTLR RuleContext for this MultiplicativeExpressionContext, providing access to the underlying ANTLR parsing information.

```go
func (s *MultiplicativeExpressionContext) GetRuleContext() antlr.RuleContext
```

--------------------------------

### FHIR Resource Test Dummies and Utilities (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/fhirtest

Provides functions to generate pseudo-randomized FHIR resource identities, construct new resources at runtime, and emulate Meta updates for R4 FHIR Protos. It organizes resources by interface abstractions and keys them by resource name.

```go
package fhirtest

import (
	"testing"

	"github.com/verily-src/fhir-go/fhir"
	"github.com/verily-src/fhir-go/fhir/resource"
	"google.golang.org/protobuf/proto"
	"github.com/verily-src/fhir-go/fhir/datatypes_go_proto"
)

var (
	// Elements is a map of all element-names to an instance of that element type.
	//
	// The elements in this map are not guaranteed to contain any specific value; 
	// it is only guaranteed to contain a non-nil instance of a concrete element
	// of the associated name.
	Elements map[string]fhir.Element

	// BackboneElements is a map of all backbone element-names to an instance of
	// that element type.
	//
	// The elements in this map are not guaranteed to contain any specific value;
	// it is only guaranteed to contain a non-nil instance of a concrete backbone
	// element of the associated name.
	BackboneElements map[string]fhir.BackboneElement
)

var CanonicalResources map[string]fhir.CanonicalResource
var DomainResources map[string]fhir.DomainResource
var MetadataResources map[string]fhir.MetadataResource
var Resources map[string]fhir.Resource

// NewResource creates a dummy resource object for the purposes of testing of type `resourceType`.
// If `resourceType` does not name a valid R4 FHIR resource, this will fail the calling test.
func NewResource(t *testing.T, resourceType resource.Type, opts ...ResourceOption) fhir.Resource

// NewResourceFromBase returns a copy of a resource modified by given options. The input resource remains unmodified.
// Useful for tweaking an existing resource for test inputs.
func NewResourceFromBase(t *testing.T, resource fhir.Resource, opts ...ResourceOption) fhir.Resource

// NewResourceOf creates a dummy resource object for the purposes of testing of type `T`.
// If `T` is not a valid FHIR R4 resource, this will fail testing.
func NewResourceOf[T fhir.Resource](t *testing.T, opts ...ResourceOption) T

// ReplaceMeta is deprecated and should use the production one in "github.com/verily-src/fhirpath-go/internal/element/meta".
func ReplaceMeta(resource fhir.Resource, m *datatypes_go_proto.Meta)

// StableRandomMeta generates a stable, pseudo-random Meta object.
func StableRandomMeta() *datatypes_go_proto.Meta

// TouchMeta updates the lastUpdated timestamp of a FHIR resource.
func TouchMeta(resource fhir.Resource)

// UpdateID updates the logical ID of a FHIR resource.
func UpdateID(resource fhir.Resource, resourceID string)

// UpdateMeta updates the versionID and lastUpdated timestamp of a FHIR resource.
func UpdateMeta(resource fhir.Resource, versionID string, updateTime time.Time)

// ResourceOption is an interface for configuring FHIR resources during creation or modification.
type ResourceOption interface {
	// Apply applies the option to the given resource.
	Apply(resource fhir.Resource)
}

// WithCodeField sets a code field on the resource.
func WithCodeField(field, value string) ResourceOption

// WithGeneratedIdentifier sets a generated identifier for the resource.
func WithGeneratedIdentifier(system string) ResourceOption

// WithJSONField sets a JSON field on the resource.
func WithJSONField(field, value string) ResourceOption

// WithProtoField sets a proto field on the resource.
func WithProtoField(field string, message proto.Message) ResourceOption

// WithRepeatedProtoField sets a repeated proto field on the resource.
func WithRepeatedProtoField(field string, messages ...proto.Message) ResourceOption

// WithResourceModification applies a custom modification function to a resource.
func WithResourceModification[T fhir.Resource](modifier func(T)) ResourceOption

```

--------------------------------

### Create Dummy FHIR Resource for Testing (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/internal/fhirtest

Creates a dummy FHIR resource of a specified R4 type for testing. If the provided resource type is not a valid R4 FHIR resource, the calling test will fail. It accepts optional ResourceOptions.

```Go
func NewResource(t *testing.T, resourceType resource.Type, opts ...ResourceOption) fhir.Resource {
  // ... implementation details ...
}
```

--------------------------------

### Expression String Representation

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/fhirpath%40v1.5_tab=versions

Provides a method to get the string representation of a compiled FHIRPath expression.

```APIDOC
## String

### Description
Returns the original FHIRPath expression string that was used to compile this `Expression` object.

### Method
`(*Expression) String`

### Parameters
#### Path Parameters
None

#### Query Parameters
None

#### Request Body
None

### Request Example
```go
// Assuming 'expr' is a compiled *fhirpath.Expression
originalExpr := expr.String()
// originalExpr now holds the FHIRPath string, e.g., "Patient.name.given"
```

### Response
#### Success Response (String)
- **string** (`string`)
  - The original FHIRPath expression string.
```

--------------------------------

### Get Relative URI String from Identity

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/resource

Returns a string representation of the relative URI for convenience.

```go
func (i *Identity) RelativeURIString() string
```

--------------------------------

### Create a Simple Resolver (Go)

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.4.0/fhirpath/resolver/resolvertest_tab=versions

Provides a function to create a simple resolver with optional configurations. The 'Entry' function allows specifying a key and resources for the resolver.

```Go
func NewSimpleResolver(opts ...SimpleResolverOption) resolver.Resolver
func Entry(key string, resources ...fhirpath.Resource) SimpleResolverOption
```

--------------------------------

### Get FHIR Resource Version ETag

Source: https://pkg.go.dev/github.com/verily-src/fhirpath-go/%40v1.0.0/internal/resource

Retrieves the ETag associated with the version of a FHIR resource.

```Go
func VersionETag(r fhir.Resource) string
```