Clear pools and terminate monitors. Topology reopens on demand.

def close(self):
        """Clear pools and terminate monitors. Topology reopens on demand."""
        with self._lock:
            for server in self._servers.values():
                server.close()

            # Mark all servers Unknown.
            self._description = self._description.reset()
            self._update_servers()
            self._opened = False

        # Publish only after releasing the lock.
        if self._publish_tp:
            self._events.put((self._listeners.publish_topology_closed,
                              (self._topology_id,)))
        if self._publish_server or self._publish_tp:
            self.__events_executor.close()