public function validatePropertyClass($input)
    {
        list($bundle, $document) = $this->parseShortcutNotation($input);

        try {
            $bundlePath = $this->getContainer()->get('kernel')->getBundle($bundle)->getPath();
        } catch (\Exception $e) {
            throw $this->getException('Bundle "%s" does not exist.', [$bundle]);
        }

        if (!file_exists($bundlePath . '/Document/' . str_replace('\\', '/', $document) . '.php')) {
            throw $this->getException('Document "%s:%s" does not exist.', [$bundle, $document]);
        }

        return $input;
    }