def _get_args(cls, args):
        # type: (tuple) -> Tuple[type, slice, Callable]
        """Return the parameters necessary to check type boundaries.

        Args:
            args: A slice representing the minimum and maximum lengths allowed
                for values of that string.

        Returns:
            A tuple with three parameters: a type, a slice, and the len
            function.
        """
        if isinstance(args, tuple):
            raise TypeError(
                "{}[...] takes exactly one argument.".format(cls.__name__)
            )
        return super(_StringMeta, cls)._get_args((_STR_TYPE, args))