docs: def add_listener(self, listener_type, callback):
          """ add a listener to the widget
              Args:
                  listener_type: string that can either be 'objectHovered' or 'objClicked' 
                  callback: python function"""
          self.listener_type= listener_type
          if listener_type == 'objectHovered':
              self.listener_callback_source_hover= callback
          elif listener_type == 'objectClicked':
              self.listener_callback_source_click= callback
          elif listener_type == 'click':
              self.listener_callback_click= callback
          elif listener_type == 'select':
              self.listener_callback_select= callback
  
          self.listener_flag= not self.listener_flag