def _get_retrier(self, receiver: Address) -> _RetryQueue:
        """ Construct and return a _RetryQueue for receiver """
        if receiver not in self._address_to_retrier:
            retrier = _RetryQueue(transport=self, receiver=receiver)
            self._address_to_retrier[receiver] = retrier
            # Always start the _RetryQueue, otherwise `stop` will block forever
            # waiting for the corresponding gevent.Greenlet to complete. This
            # has no negative side-effects if the transport has stopped because
            # the retrier itself checks the transport running state.
            retrier.start()
        return self._address_to_retrier[receiver]
Construct and return a _RetryQueue for receiver