code: def _process_periodic_tasks(self):
          
          address_to_cursor_ids = defaultdict(list)
  
          # Other threads or the GC may append to the queue concurrently.
          while True:
              try:
                  address, cursor_ids = self.__kill_cursors_queue.pop()
              except IndexError:
                  break
  
              address_to_cursor_ids[address].extend(cursor_ids)
  
          # Don't re-open topology if it's closed and there's no pending cursors.
          if address_to_cursor_ids:
              topology = self._get_topology()
              for address, cursor_ids in address_to_cursor_ids.items():
                  try:
                      self._kill_cursors(
                          cursor_ids, address, topology, session=None)
                  except Exception:
                      helpers._handle_exception()
          try:
              self._topology.update_pool()
          except Exception:
              helpers._handle_exception()
docs: Process any pending kill cursors requests and
          maintain connection pool parameters.