code: def get_connection_id_by_endpoint(self, endpoint):
          
          with self._connections_lock:
              for connection_id in self._connections:
                  connection_info = self._connections[connection_id]
                  if connection_info.uri == endpoint:
                      return connection_id
              raise KeyError()
docs: Returns the connection id associated with a publically
          reachable endpoint or raises KeyError if the endpoint is not
          found.
  
          Args:
              endpoint (str): A zmq-style uri which identifies a publically
                  reachable endpoint.