this is a no-op. If both are not specified, the return value of
    :func:`default_tolerances` is used.

    Raises:
        ErrorMeta: With :class:`ValueError`, if only ``rtol`` or ``atol`` is specified.

    Returns:
        (Tuple[float, float]): Valid absolute and relative tolerances.
    NzGBoth 'rtol' and 'atol' must be either specified or omitted, but got no rE