public function addVideoDeveloperTag($developerTag)
    {
        $this->ensureMediaGroupIsNotNull();
        $newCategory = new Zend_Gdata_Media_Extension_MediaCategory($developerTag, self::YOUTUBE_DEVELOPER_TAGS_SCHEMA);

        if ($this->getMediaGroup()->getCategory() == null) {
            $this->getMediaGroup()->setCategory($newCategory);
        } else {
            $categories = $this->getMediaGroup()->getCategory();
            $categories[] = $newCategory;
            $this->getMediaGroup()->setCategory($categories);
        }
        return $this;
    }