code: def if_mousedown(handler):
      
      def handle_if_mouse_down(mouse_event):
          if mouse_event.event_type == MouseEventType.MOUSE_DOWN:
              return handler(mouse_event)
          else:
              return NotImplemented
      return handle_if_mouse_down
docs: Decorator for mouse handlers.
      Only handle event when the user pressed mouse down.
  
      (When applied to a token list. Scroll events will bubble up and are handled
      by the Window.)