docs: def add_converter(cls, klass, conv, score=0):
          """ Add converter
          :param klass: class or str
          :param conv: callable
          :param score:
          :return:
          """
          if isinstance(klass, str):
              klass = import_name(klass)
          item = klass, conv, score
          cls.converters.append(item)
          cls.converters.sort(key=lambda x: x[0])
          return cls