code: def pad_ends(
      sequence,
      pad_left=True,
      left_pad_symbol="<s>",
      right_pad_symbol="</s>",
  ):
      """
      Pad sentence ends with start- and end-of-sentence tokens
  
      In speech recognition, it is important to predict the end of sentence
      and use the start of sentence to condition predictions. Typically this
      is done by adding special tokens (usually <s> and </s>) at the ends of
      each sentence. The <s> token should not be predicted, so some special
      care needs to be taken for unigrams.
  
      Arguments
      ---------
      sequence : iterator
          The sequence (any iterable type) to pad.
      pad_left : bool
          Whether to pad on the left side as well. True by default.
      left_pad_symbol : any
          The token to use for left side padding. "<s>" by default.
      right_pad_symbol : any
          The token to use for right side padding. "</s>" by default.
  
      Returns
      -------
      generator
          A generator that yields the padded sequence.
  
      Example
      -------
      >>> for token in pad_ends(["Speech", "Brain"]):
      ...     print(token)
      <s>
      Speech
      Brain
      </s>
  
      """
      if pad_left:
          return itertools.chain(
              (left_pad_symbol,), tuple(sequence), (right_pad_symbol,)
          )
      else:
          return itertools.chain(tuple(sequence), (right_pad_symbol,))
  
imports: import itertools
label_desc: Use image node_id 1 for calling a global function with example usage: pad_ends(sequence, pad_left, left_pad_symbol, right_pad_symbol) and returns: itertools, itertools