code: def _queuer(instances: Iterable[Instance],
              input_queue: Queue,
              num_workers: int,
              num_epochs: Optional[int]) -> None:
      
      epoch = 0
  
      while num_epochs is None or epoch < num_epochs:
          epoch += 1
          for instance in instances:
              input_queue.put(instance)
  
      # Now put a None for each worker, since each needs to receive one
      # to know that it's done.
      for _ in range(num_workers):
          input_queue.put(None)
docs: Reads Instances from the iterable and puts them in the input_queue.