code: protected void setMapLayerAt(int index, L layer) {
  		this.subLayers.set(index, layer);
  		layer.setContainer(this);
  		resetBoundingBox();
  	}
docs: Put the given layer at the given index but
  do not fire any event.
  
  <p>This function does not test if the layer
  is already present in the list of layers.
  
  @param index index.
  @param layer layer.
  @throws IndexOutOfBoundsException if the index
  is invalid.