code: def type(subtag, type):
          
          subtag = subtag.lower()
          if subtag in index:
              types = index[subtag]
              if type in types:
                  return Subtag(subtag, type)
          return None
docs: Get a :class:`language_tags.Subtag.Subtag` by subtag and type. Can be None if not exists.
  
          :param str subtag: subtag.
          :param str type: type of the subtag.
          :return: :class:`language_tags.Subtag.Subtag` if exists, otherwise None.