code: def _closest_ref_length(references, trans_length):
      
      ref_lengths = (len(reference) for reference in references)
      closest_ref_len = min(ref_lengths,
                            key=lambda ref_length: (abs(ref_length - trans_length), ref_length))
  
      return closest_ref_len
docs: Find the reference that has the closest length to the translation.
  
      Parameters
      ----------
      references: list(list(str))
          A list of references.
      trans_length: int
          Length of the translation.
  
      Returns
      -------
      closest_ref_len: int
          Length of the reference that is closest to the translation.