code: def pick_coda_from_letter(letter):
      
      try:
          __, __, coda = \
              split_phonemes(letter, onset=False, nucleus=False, coda=True)
      except ValueError:
          return None
      else:
          return coda
docs: Picks only a coda from a Hangul letter.  It returns ``None`` if the
      given letter is not Hangul.