code: def _build_synset_lookup(imagenet_metadata_file):
    
    lines = tf.gfile.FastGFile(imagenet_metadata_file, 'r').readlines()
    synset_to_human = {}
    for l in lines:
      if l:
        parts = l.strip().split('\t')
        assert len(parts) == 2
        synset = parts[0]
        human = parts[1]
        synset_to_human[synset] = human
    return synset_to_human
docs: Build lookup for synset to human-readable label.
  
    Args:
      imagenet_metadata_file: string, path to file containing mapping from
        synset to human-readable label.
  
        Assumes each line of the file looks like:
  
          n02119247    black fox
          n02119359    silver fox
          n02119477    red fox, Vulpes fulva
  
        where each line corresponds to a unique mapping. Note that each line is
        formatted as <synset>\t<human readable label>.
  
    Returns:
      Dictionary of synset to human labels, such as:
        'n02119022' --> 'red fox, Vulpes vulpes'