public function getUserFeed($userName = null, $location = null)
    {
        if ($location instanceof Zend_Gdata_Photos_UserQuery) {
            $location->setType('feed');
            if ($userName !== null) {
                $location->setUser($userName);
            }
            $uri = $location->getQueryUrl();
        } else if ($location instanceof Zend_Gdata_Query) {
            if ($userName !== null) {
                $location->setUser($userName);
            }
            $uri = $location->getQueryUrl();
        } else if ($location !== null) {
            $uri = $location;
        } else if ($userName !== null) {
            $uri = self::PICASA_BASE_FEED_URI . '/' .
                self::DEFAULT_PROJECTION . '/' . self::USER_PATH . '/' .
                $userName;
        } else {
            $uri = self::PICASA_BASE_FEED_URI . '/' .
                self::DEFAULT_PROJECTION . '/' . self::USER_PATH . '/' .
                self::DEFAULT_USER;
        }

        return parent::getFeed($uri, 'Zend_Gdata_Photos_UserFeed');
    }