Queue a request to be sent to the RPC.

def send(self, request):
        """Queue a request to be sent to the RPC."""
        if self._UNARY_REQUESTS:
            try:
                self._send_unary_request(request)
            except exceptions.GoogleAPICallError:
                _LOGGER.debug(
                    "Exception while sending unary RPC. This is typically "
                    "non-fatal as stream requests are best-effort.",
                    exc_info=True,
                )
        else:
            self._rpc.send(request)