code: function EquirectGeometry(levelPropertiesList) {
    if (type(levelPropertiesList) !== 'array') {
      throw new Error('Level list must be an array');
    }
  
    this.levelList = common.makeLevelList(levelPropertiesList, EquirectLevel);
    this.selectableLevelList = common.makeSelectableLevelList(this.levelList);
  }
docs: @class EquirectGeometry
  @implements Geometry
  @classdesc
  
  A {@link Geometry} implementation suitable for equirectangular images with a
  2:1 aspect ratio.
  
  @param {Object[]} levelPropertiesList Level description
  @param {number} levelPropertiesList[].width Level width in pixels