code: def hcj_to_jamo(hcj_char, position="vowel"):
      
      if position == "lead":
          jamo_class = "CHOSEONG"
      elif position == "vowel":
          jamo_class = "JUNGSEONG"
      elif position == "tail":
          jamo_class = "JONGSEONG"
      else:
          raise InvalidJamoError("No mapping from input to jamo.", hcj_char)
      jamo_name = re.sub("(?<=HANGUL )(\w+)",
                         jamo_class,
                         _get_unicode_name(hcj_char))
      # TODO: add tests that test non entries.
      if jamo_name in _JAMO_REVERSE_LOOKUP.keys():
          return _JAMO_REVERSE_LOOKUP[jamo_name]
      return hcj_char
docs: Convert a HCJ character to a jamo character.
      Arguments may be single characters along with the desired jamo class
      (lead, vowel, tail). Non-mappable input will raise an InvalidJamoError.