In many Cesium sandbox examples such as this one a CZML file is loaded in its entirety. Is there any way to loop through the elements in the CZML file and load them individually?

My aim is to add a checkbox for each element so I can enable/disable them at will

Currently the code that loads the data works as follows however nothing is loaded:

for(let i = 0; i <entireDataSource.entities.length; i++){
    var seriesName = entireDataSource.entities[i].id;
    
    var newLi = document.createElement('li');
    var newInput = document.createElement('input');

    newInput.setAttribute('type', 'checkbox');
    newInput.setAttribute('id', seriesName);      

    newLi.appendChild(newInput);
  
    newLi.appendChild(document.createTextNode(seriesName));
    
    checkboxList.appendChild(newLi);}

I have tried creating the checkboxes with no data and just filing them with a incremental number and that worked, so it is the data failing to load that is causing the issue.

Any idea why nothing is loaded?

Additionally - is there anyway to print info to the sandcastle console for debugging purposes?