docs: def save(f, arr, vocab):
      """
      Save word embedding file.
  
      Args:
          f (File): File to write the vectors. File should be open for writing
              ascii.
          arr (numpy.array): Numpy array with ``float`` dtype.
          vocab (iterable): Each element is pair of a word (``bytes``) and ``arr``
              index (``int``). Word should be encoded to str apriori.
      """
      itr = iter(vocab)
      # Avoid empty line at the end
      word, idx = next(itr)
      _write_line(f, arr[idx], word)
      for word, idx in itr:
          f.write(b'\n')
          _write_line(f, arr[idx], word)