code: def _add_export(self, ed_id, inst):
          # type: (str, Tuple[Any, EndpointDescription]) -> None
          
          with self._exported_instances_lock:
              self._exported_services[ed_id] = inst
docs: Keeps track of an exported service
  
          :param ed_id: ID of the endpoint description
          :param inst: A tuple: (service instance, endpoint description)