protected function getIdsOfServicesThatAreDefinedInApplication()
    {
        if ($this->serviceIdWhitelist === null) {
            $builder = $this->createContainerBuilder();
            $this->applyToExtensions(function (ExtensionInterface $extension) use ($builder) {
                $extension->load($builder->getExtensionConfig($extension->getAlias()), $builder);
            });
            $this->serviceIdWhitelist = $builder->getServiceIds();
        }
        return $this->serviceIdWhitelist;
    }