docs: def _queue_manangement_worker(executor_reference,
                                processes,
                                pending_work_items,
                                work_ids_queue,
                                call_queue,
                                result_queue,
                                shutdown_process_event):
      """Manages the communication between this process and the worker processes.
  
      This function is run in a local thread.
  
      Args:
          executor_reference: A weakref.ref to the ProcessPoolExecutor that owns
              this thread. Used to determine if the ProcessPoolExecutor has been
              garbage collected and that this function can exit.
          process: A list of the multiprocessing.Process instances used as
              workers.
          pending_work_items: A dict mapping work ids to _WorkItems e.g.
              {5: <_WorkItem...>, 6: <_WorkItem...>, ...}
          work_ids_queue: A queue.Queue of work ids e.g. Queue([5, 6, ...]).
          call_queue: A multiprocessing.Queue that will be filled with _CallItems
              derived from _WorkItems for processing by the process workers.
          result_queue: A multiprocessing.Queue of _ResultItems generated by the
              process workers.
          shutdown_process_event: A multiprocessing.Event used to signal the
              process workers that they should exit when their work queue is
              empty.
      """
      while True:
          _add_call_item_to_queue(pending_work_items,
                                  work_ids_queue,
                                  call_queue)
  
          try:
              result_item = result_queue.get(block=True, timeout=0.1)
          except queue.Empty:
              executor = executor_reference()
              # No more work items can be added if:
              #   - The interpreter is shutting down OR
              #   - The executor that owns this worker has been collected OR
              #   - The executor that owns this worker has been shutdown.
              if _shutdown or executor is None or executor._shutdown_thread:
                  # Since no new work items can be added, it is safe to shutdown
                  # this thread if there are no pending work items.
                  if not pending_work_items:
                      shutdown_process_event.set()
  
                      # If .join() is not called on the created processes then
                      # some multiprocessing.Queue methods may deadlock on Mac OSX.
                      for p in processes:
                          p.join()
                      return
              del executor
          else:
              work_item = pending_work_items.pop(result_item.work_id)
              loop = work_item.loop
              loop.call_from_thread(_set_work_result, work_item, result_item)
              del result_item, work_item, loop