protected function getSectionClassName(string $name) : string {
        $className = sprintf(
            '%s\\%s',
            get_class($this),
            ucfirst($name)
        );

        if (! class_exists($className)) {
            throw new \RuntimeException(
                sprintf(
                    'Invalid section name "%s" (%s)',
                    $name,
                    $className
                )
            );
        }

        return $className;
    }