code: def _download_multiprocess_map_chunk(pool_tup):
      """
      Helper function for Pool imap_unordered.
  
      Apparently function must be pickable (which apparently means must be
      defined at the top level of a module and can't be a lamdba) to be used in
      imap_unordered. Has to do with how it's passed to the subprocess.
  
      :param pool_tup: is a tuple where first arg is an array of tuples of url
      and dest file name for the current chunk and second arg is function to be
      called.
      :return: an array of tuples
      """
      items = pool_tup[0]
      path = pool_tup[1]
      fn = pool_tup[2]
      return [fn(it[0], path, it[1]) for it in items]
  
imports: import importlib
  import json
  import time
  import datetime
  import os
  import requests
  import shutil
  import hashlib
  import tqdm
  import gzip
  import math
  import contextlib
  import parlai.utils.logging
  from parlai.utils.io import PathManager
label_desc: Use image node_id 16 for calling a global function with example usage: _download_multiprocess_map_chunk(pool_tup) and returns: unknown