private function storeCustomMetaData($customMetaData, $videoId)
    {
        // only update custom meta data fields related to rating
        $this->client->setCustomMetaData(
            $this->vmId,
            $videoId,
            $this->filterCustomMetaData($customMetaData)
        );

        // also store custom meta data fields locally, if video is fetched again by function $this->getVideo($videoId)
        $this->getVideo($videoId)->setCustomMetadata($customMetaData);
    }