code: def _default_unk_index():
      return 0
  
imports: from __future__ import unicode_literals
  import array
  from collections import defaultdict
  import io
  import logging
  import os
  import zipfile
  import six
  from six.moves.urllib.request import urlretrieve
  import torch
  from tqdm import tqdm
  import tarfile
  from .utils import reporthook
label_desc: Use image node_id 1 for calling a global function with example usage: _default_unk_index() and returns: int