docs: async def stop(self):
          """
          Stop and close the DTLS transport.
          """
          if self._task is not None:
              self._task.cancel()
              self._task = None
  
          if self._state in [State.CONNECTING, State.CONNECTED]:
              lib.SSL_shutdown(self.ssl)
              try:
                  await self._write_ssl()
              except ConnectionError:
                  pass
              self.__log_debug('- DTLS shutdown complete')