### lazySizes Library Core Implementation Source: https://cichpack.com/product-category/cubitainer/ The core implementation of the lazySizes library, including its initialization, observer setup, and handling of various image and element loading scenarios. It supports IntersectionObserver and provides fallback mechanisms. ```javascript (function(e,t,r){ if(typeof module=="object"&&module.exports){ module.exports=lazySizes }else{ e.lazySizes=t(e,e.document,Date) } })(window,function e(e,t,r){ "use strict"; if(!e.IntersectionObserver||!t.getElementsByClassName||!e.MutationObserver){ return } var i,n; var a=t.documentElement; var s=e.HTMLPictureElement; var o="addEventListener"; var l="getAttribute"; var c=e[o].bind(e); var u=e.setTimeout; var f=e.requestAnimationFrame||u; var d=e.requestIdleCallback||u; var v=/^picture$/i; var m=["load","error","lazyincluded","_lazyloaded"]; var g=Array.prototype.forEach; var p=function(e,t){return e.classList.contains(t)}; var z=function(e,t){e.classList.add(t)}; var h=function(e,t){e.classList.remove(t)}; var y=function(e,t,r){ var i=r?o:"removeEventListener"; if(r){ y(e,t) } m.forEach(function(r){ e[i](r,t) }) }; var b=function(t,r,n,a,s){ var o=t.createEvent("CustomEvent"); if(!n){ n={} } n.instance=i; o.initCustomEvent(r,!a,!s,n); e.dispatchEvent(o); return o }; var C=function(t,r){ var i; if(!s&&(i=e.picturefill||n.pf)){ i({reevaluate:true,elements:[t]}) }else if(r&&r.src){ t.src=r.src } }; var w=function(e,t){return(getComputedStyle(e,null)||{})[t]}; var E=function(e,t,r){ r=r||e.offsetWidth; while(r49?function(){ d(a,{timeout:n.ricTimeout}); if(n.ricTimeout!==n.ricTimeout){ n.ricTimeout=n.ricTimeout } }:x(function(){ u(a,true) },true); return function(e){ var n; if(e=e===true){ n.ricTimeout=33 } if(t){ return } t=true; n=n.throttleDelay-(r.now()-i); if(n<0){ n=0 } if(e||n<9){ s() }else{ u(s,n) } } }; var T=function(e){ var t,i; var n=99; var a=function(){ t=null; e() }; var s=function(){ var e=r.now()-i; if(e