private function createClient($config)
    {
        $keyFile = array_get($config, 'key_file');
        if (is_string($keyFile)) {
            return new StorageClient([
                'projectId' => $config['project_id'],
                'keyFilePath' => $keyFile,
            ]);
        }

        if (! is_array($keyFile)) {
            $keyFile = [];
        }
        return new StorageClient([
            'projectId' => $config['project_id'],
            'keyFile' => array_merge(["project_id" => $config['project_id']], $keyFile)
        ]);
    }