code: public void addItem(Point coordinates, Drawable item) {
  	assertEDT();
  	if (coordinates == null || item == null) {
  	    throw new IllegalArgumentException("Coordinates and added item cannot be null");
  	}
  	log.trace("[addItem] New item added @ {}", coordinates);
  	getPanelAt(coordinates).addModel(item);
  	getPanelAt(coordinates).repaint();
  
      }
docs: Adds an item to draw in a particular position
  
  @param coordinates the position of the item
  @param item the drawable element