code: function WebGLRenderGroup(gl, transparent)
  {
      this.gl = gl;
      this.root = null;
  
      this.backgroundColor = undefined;
      this.transparent = transparent === undefined ? true : transparent;
  
      this.batchs = [];
      this.toRemove = [];
      //console.log(this.transparent);
      this.filterManager = new WebGLFilterManager(this.transparent);
  }
docs: A WebGLBatch Enables a group of sprites to be drawn using the same settings.
  if a group of sprites all have the same baseTexture and blendMode then they can be
  grouped into a batch. All the sprites in a batch can then be drawn in one go by the
  GPU which is hugely efficient. ALL sprites in the webGL renderer are added to a batch
  even if the batch only contains one sprite. Batching is handled automatically by the
  webGL renderer. A good tip is: the smaller the number of batchs there are, the faster
  the webGL renderer will run.
  
  @class WebGLBatch
  @contructor
  @param gl {WebGLContext} An instance of the webGL context