private function getDefinitionsFilePath(array $config)
    {
        $filePath = __DIR__ . '/../../../../../../../config/php-di.config.php';

        if (isset($config['definitionsFile'])) {
            $filePath = $config['definitionsFile'];
        }

        if (!file_exists($filePath)) {
            throw new \Exception('DI definitions file missing.');
        }

        return $filePath;
    }