SIgma.js - Container not found inside an iframe

with Sigma.js I am trying to make it work within an iframe, I get the error Container not found , it does not recognize the div with id="graphContainer" with which sigma renders the graphics. the iframe belongs to an Ifobox belonging to another library cesium.js . so I am modifying the iframe with jquery . if I can modify the iframe but sigma.js does not recognize the sun that I insert the iframe.

I define that it is asynchronous requested by jquery

  $.ajaxPrefilter(function (options, original_Options, jqXHR) {
  options.async = true;
});

I select the iframe

var $iframe = $('.cesium-infoBox-iframe');

I do not know why but if I do not do it with ready I get another error

  $iframe.ready(function () {

 // inserto la libreria sigma.js en el hean del iframe

  var js_iframe = document.createElement('script');
  js_iframe.setAttribute('src', 'sigma.min.js');
  $iframe.contents().find("head").append(js_iframe);

  // inserto el div contenedor para sigma, dentro de otro div ya existente en el body del iframe

  var js_iframe2 = document.createElement('div');
  js_iframe2.setAttribute('id', 'graphContainer');
  $iframe.contents().find(".cesium-infoBox-description").append(js_iframe2);

  // inserto el fichero  sigma_infobox.js abajo del div de id="graphContainer" dentro del div ya existente en el iframe

  var js_iframe3 = document.createElement('script');
  js_iframe3.setAttribute('src', 'sigma_infobox.js');
  $iframe.contents().find(".cesium-infoBox-description").append(js_iframe3);



    });

the file sigma_infobox.js

"use strict";

var s = new sigma('graphContainer');

//set some default graph settings
s.settings({
    defaultNodeColor: '#f00',
    edgeColor: '#000'
});

//manually build up a graph from nodes and edges
s.graph.addNode({
    id: 'node0',
    label: 'Foo',
    x: 0,
    y: 0,
    size: 1
});

 s.graph.addNode({
 id: 'node1',
 label: 'Bar',
 x: 1,
 y: 0,
 size: 1
 });

 s.graph.addEdge({
 id: 'edge0',
 source: 'node0',
 target: 'node1',
 });*/

s.refresh();