public function get($serviceName) {
        $container = $this->serviceData[$serviceName] ?? NULL;
        if($container) {
            return $container->getInstance();
        }

        if(in_array($serviceName, $this->getSelfReferenceNames()))
            return $this;

        $e = new UnknownServiceException("Service $serviceName is not registered", E_USER_ERROR);
        $e->setServiceName($serviceName);
        throw $e;
    }