code: def _replace_oov(original_vocab, line):
    
    return u" ".join(
        [word if word in original_vocab else u"UNK" for word in line.split()])
docs: Replace out-of-vocab words with "UNK".
  
    This maintains compatibility with published results.
  
    Args:
      original_vocab: a set of strings (The standard vocabulary for the dataset)
      line: a unicode string - a space-delimited sequence of words.
  
    Returns:
      a unicode string - a space-delimited sequence of words.