protected function searchExtractorClassInLib($serviceFullyQualifiedClass)
    {
        $parts = explode('\\', $serviceFullyQualifiedClass);
        $className = $parts[ sizeof($parts) - 1 ];

        $extractorClass = sprintf('\OAuth\UserData\Extractor\%s', $className);
        if (class_exists($extractorClass)) {
            return $extractorClass;
        }

        return null;
    }