code: public List<VectorLayer> getVectorLayers() {
  		ArrayList<VectorLayer> list = new ArrayList<VectorLayer>();
  		for (Layer<?> layer : layers) {
  			if (layer instanceof VectorLayer) {
  				list.add((VectorLayer) layer);
  			}
  		}
  		return list;
  	}
docs: Return a list containing all vector layers within this model.
  
  @return vector layers