SimplePie_Item::get_link

	 * @since Beta 3
	 * @param int $key The link that you want to return.  Remember that arrays begin with 0, not 1
	 * @param string $rel The relationship of the link to return
	 * @return string|null Link URL
	 */
	public function get_link($key = 0, $rel = 'alternate')
	{
		$links = $this->get_links($rel);
		if ($links && $links[$key] !== null)
		{
			return $links[$key];
		}