code: def register_on_extra_data_can_change(self, callback):
          
          event_type = library.VBoxEventType.on_extra_data_can_change
          return self.event_source.register_callback(callback, event_type)
docs: Set the callback function to consume on extra data changed
          events.
  
          Callback receives a IExtraDataCanChangeEvent object.
  
          Returns the callback_id