constructor(parent) {
    super(parent)
    this._orderedItemKeys = []
  }
ListFacade is an optimized way to define a large number of scene objects based on an array of data.
Unlike mapping a data array to `children` objects in the scene descriptor, ListFacade allows you to
define only a single "template" descriptor object whose properties are either constant values
or accessor functions that get invoked for each data item. The resulting property values are
then applied directly to the implementation objects, without creating any intermediary objects.

Example:

    {
      key: 'balls',
      facade: ListFacade,
      data: itemsData,
      template: {
        key: (item, i, all) => `ball_${ item.id }`,
        facade: Ball,
        x: (item, i, all) => item.time,
        y: (item, i, all) => item.count,
        radius: 10,
        color: (item, i, all) => item.important ? 0xff0000 : 0xcccccc
      }
    }