Contao\CoreBundle\DataContainer\PaletteManipulator::validatePosition PHP Метод

    private function validatePosition($position)
    {
        static $positions = [self::POSITION_BEFORE, self::POSITION_AFTER, self::POSITION_PREPEND, self::POSITION_APPEND];
        if (!in_array($position, $positions, true)) {
            throw new PalettePositionException('Invalid legend position');
        }
    }