code: def _close_cursor(self, cursor_id, address):
          
          if self.__cursor_manager is not None:
              self.__cursor_manager.close(cursor_id, address)
          else:
              self.__kill_cursors_queue.append((address, [cursor_id]))
docs: Send a kill cursors message with the given id.
  
          What closing the cursor actually means depends on this client's
          cursor manager. If there is none, the cursor is closed asynchronously
          on a background thread.