public function createService($serviceClass)
    {
        $className = $serviceClass;
        if (!$this->isNamespacedClass($serviceClass)) {
            // Used for backwards compatibility.
            $className = $this->formClassName($serviceClass);
        }
        if (!class_exists($className)) {
            throw new Exception("Service '$serviceClass' was not found!");
        }
        $service = new $className($this->getServiceConfig());

        if (!($service instanceof ShopServiceInterface)) {
            throw new Exception("Service '$className' does not implement ShopServiceInterface interface!");
        }

        return $service;
    }