### Arena Tree Operations

Source: https://docs.rs/indextree

Examples of creating an arena, adding nodes, and performing tree operations like appending.

```APIDOC
## Arena Tree Operations

### Description
Demonstrates how to initialize an Arena and perform basic node manipulation such as adding nodes and appending them.

### Request Example
```rust
use indextree::Arena;

// Create a new arena
let arena = &mut Arena::new();

// Add some new nodes to the arena
let a = arena.new_node(1);
let b = arena.new_node(2);

// Append b to a
a.append(b, arena);
assert_eq!(b.ancestors(arena).count(), 2);
```
```

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

### Create and Append Nodes in Arena

Source: https://docs.rs/indextree

Demonstrates the basic usage of creating an arena, adding new nodes, and appending one node to another. Ensure the arena is mutable when performing append operations.

```rust
use indextree::Arena;

// Create a new arena
let arena = &mut Arena::new();

// Add some new nodes to the arena
let a = arena.new_node(1);
let b = arena.new_node(2);

// Append b to a
a.append(b, arena);
assert_eq!(b.ancestors(arena).count(), 2);
```

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

### Checked Tree Mutation

Source: https://docs.rs/indextree

Demonstrates error handling using checked variants of tree modification methods.

```APIDOC
## Checked Tree Mutation

### Description
Methods that modify the tree come in checked variants that return a Result with a NodeError on failure, preventing panics.

### Request Example
```rust
use indextree::{Arena, NodeError};

let mut arena = Arena::new();
let root = arena.new_node("root");

// Cannot append a node to itself
assert!(matches!(
    root.checked_append(root, &mut arena),
    Err(NodeError::AppendSelf)
));
```
```

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

### Handle Node Append Errors

Source: https://docs.rs/indextree

Illustrates how to use the checked variants of tree mutation methods to handle errors, such as attempting to append a node to itself. The `checked_append` method returns a `Result` which can be matched for specific `NodeError` variants.

```rust
use indextree::{Arena, NodeError};

let mut arena = Arena::new();
let root = arena.new_node("root");

// Cannot append a node to itself
assert!(matches!(
    root.checked_append(root, &mut arena),
    Err(NodeError::AppendSelf)
));
```

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