code: public Layer getLayer(String layerId) {
  		org.geomajas.gwt.client.map.layer.Layer<?> layer = mapModel.getLayer(layerId);
  		if (layer instanceof org.geomajas.gwt.client.map.layer.VectorLayer) {
  			return new VectorLayer((org.geomajas.gwt.client.map.layer.VectorLayer) layer);
  		}
  		return new LayerImpl(layer);
  	}
docs: Get a single layer by its identifier.
  
  @param id
  The layers unique identifier within this map.
  @return Returns the layer, or null if it could not be found.