def _request_check(self, address):
        """Wake one monitor. Hold the lock when calling this."""
        server = self._servers.get(address)

        # "server" is None if another thread removed it from the topology.
        if server:
            server.request_check()
Wake one monitor. Hold the lock when calling this.
stackoverflow/venv/lib/python3.6/site-packages/pymongo/topology.py