private function createSoapHeaderObject(
        AdsServiceDescriptor $serviceDescriptor
    ) {
        // The SOAP header object is in the same base namespace (without the group)
        // as the AdWords service we are generating headers for.
        $reflectionClass =
            new ReflectionClass($serviceDescriptor->getServiceClass());
        $namespaceParts =
            explode('\\', trim($reflectionClass->getNamespaceName(), '\\'));
        // Remove the group.
        array_pop($namespaceParts);
        $soapHeaderClassName = sprintf(
            '%s\\%s',
            implode('\\', $namespaceParts),
            self::DEFAULT_SOAP_HEADER_CLASS_NAME
        );

        return $this->reflection->createInstance($soapHeaderClassName);
    }