code: def _process_worker(call_queue, result_queue):
      
      while True:
          call_item = call_queue.get(block=True)
          if call_item is None:
              # Wake up queue management thread
              result_queue.put(None)
              return
          try:
              r = call_item.fn(*call_item.args, **call_item.kwargs)
          except BaseException:
              e = sys.exc_info()[1]
              result_queue.put(_ResultItem(call_item.work_id,
                                           exception=e))
          else:
              result_queue.put(_ResultItem(call_item.work_id,
                                           result=r))
docs: Evaluates calls from call_queue and places the results in result_queue.
  
      This worker is run in a separate process.
  
      Args:
          call_queue: A multiprocessing.Queue of _CallItems that will be read and
              evaluated by the worker.
          result_queue: A multiprocessing.Queue of _ResultItems that will written
              to by the worker.
          shutdown: A multiprocessing.Event that will be set as a signal to the
              worker that it should exit when call_queue is empty.