code: def show_message(self, message_str):
          
          if self._message_handle is not None:
              self._message_handle.cancel()
          self._message_handle = asyncio.get_event_loop().call_later(
              self._MESSAGE_DELAY_SECS, self._clear_message
          )
          self._message = message_str
          self._update()
docs: Show a temporary message.