public static function guardAgainstInvalidNumeric($numeric)
    {
        if (!is_string($numeric)) {
            throw new InvalidArgumentException(
                sprintf('Expected $numeric to be of type string, got: %s', gettype($numeric))
            );
        }

        if (!preg_match('/^[0-9]{3}$/', $numeric)) {
            throw new DomainException(
                sprintf('Not a valid numeric key: %s', $numeric)
            );
        }
    }