async def wait_for_request_iterator_stop(self):
        """Wait for the request iterator to stop.

        This must be called from a duet thread.
        """
        await self._request_iterator_stopped
        self._request_iterator_stopped = duet.AwaitableFuture()
Wait for the request iterator to stop.

        This must be called from a duet thread.
        
cirq-google/cirq_google/engine/stream_manager_test.py