code: def _get_names(dirs):
    
    alphabets = set()
    label_names = {}
    for d in dirs:
      for example in _walk_omniglot_dir(d):
        alphabet, alphabet_char_id, label, _ = example
        alphabets.add(alphabet)
        label_name = "%s_%d" % (alphabet, alphabet_char_id)
        if label in label_names:
          assert label_names[label] == label_name
        else:
          label_names[label] = label_name
    label_names = [label_names[k] for k in sorted(label_names)]
    return alphabets, label_names
docs: Get alphabet and label names, union across all dirs.