code: def copy_callback(task_queue, res_queue, num_samples):
      msgs = task_queue.get(num_samples=num_samples)
      if msgs is None:
          return
      assert len(msgs) > 0
      res_queue.put(msgs)
      return msgs
  
imports: import os
  import multiprocessing
  import socket
  from contextlib import closing, contextmanager
  import numpy
  from nvidia.dali._multiproc.shared_batch import BufShmChunk, SharedBatchWriter, SharedBatchMeta, deserialize_batch
  from nvidia.dali._multiproc.shared_queue import ShmQueue
  from nvidia.dali._multiproc.messages import ShmMessageDesc
  from test_utils import RandomlyShapedDataIterator
  from nose_utils import raises
label_desc: Use image node_id 8 for calling a global function with example usage: copy_callback(task_queue, res_queue, num_samples) and returns: msgs