code: private int rasterLayerCount() {
  		int rasterLayerCount = 0;
  		for (int index = 0; index < mapInfo.getLayers().size(); index++) {
  			if (layers.get(index) instanceof RasterLayer) {
  				rasterLayerCount++;
  			}
  		}
  		return rasterLayerCount;
  	}
docs: Count the total number of raster layers in this model.
  
  @return number of raster layers