public function actionKeywords($topicId)
 {
     $model = Topic::findOne($topicId);
     if (!isset($model)) {
         throw new \Exception('Topic ID does not correspond to a database-entry');
     }
     $client = new Client();
     $keywordData = $client->getTopicKeywords($topicId);
     foreach ($keywordData as $keyword) {
         $this->_syncKeyword($keyword);
         $model->linkKeyword($keyword);
     }
     return 0;
 }