SimplePie::get_contributors

	 */
	public function get_category($key = 0)
	{
		$categories = $this->get_categories();
		if (isset($categories[$key]))
		{
			return $categories[$key];
		}

		return null;
	}

	/**
	 * Get all categories for the feed
	 *
	 * Uses `<atom:category>`, `<category>` or `<dc:subject>`
	 *
	 * @since Unknown
	 * @return array|null List of {@see SimplePie_Category} objects
	 */
	public function get_categories()
	{
		$categories = array();

		foreach ((array) $this->get_channel_tags(SIMPLEPIE_NAMESPACE_ATOM_10, 'category') as $category)
		{
			$term = null;
			$scheme = null;
			$label = null;
			if (isset($category['attribs']['']['term']))
			{
				$term = $this->sanitize($category['attribs']['']['term'], SIMPLEPIE_CONSTRUCT_TEXT);
			}
			if (isset($category['attribs']['']['scheme']))
			{
				$scheme = $this->sanitize($category['attribs']['']['scheme'], SIMPLEPIE_CONSTRUCT_TEXT);
			}
			if (isset($category['attribs']['']['label']))
			{
				$label = $this->sanitize($category['attribs']['']['label'], SIMPLEPIE_CONSTRUCT_TEXT);
			}
			$categories[] = $this->registry->create('Category', array($term, $scheme, $label));
		}
		foreach ((array) $this->get_channel_tags(SIMPLEPIE_NAMESPACE_RSS_20, 'category') as $category)
		{
			// This is really the label, but keep this as the term also for BC.
			// Label will also work on retrieving because that falls back to term.
			$term = $this->sanitize($category['data'], SIMPLEPIE_CONSTRUCT_TEXT);
			if (isset($category['attribs']['']['domain']))
			{
				$scheme = $this->sanitize($category['attribs']['']['domain'], SIMPLEPIE_CONSTRUCT_TEXT);
			}
			else
			{
				$scheme = null;
			}
			$categories[] = $this->registry->create('Category', array($term, $scheme, null));