public function AddTag($tag)
    {
        $this->tag = $tag;
        $response = $this->doPost('/library/' . $this->mediaId . '/tag', [
            'tag' => [$tag]
        ]);

        $tags = $this->hydrate($response);
        foreach ($response['tags'] as $item) {
            $tag = new XiboLibrary($this->getEntityProvider());
            $tag->hydrate($item);
            $tags->tags[] = $tag;
        }
        return $this;
    }