public function getActivityForUser($username)
    {
        if ($this->getMajorProtocolVersion() == 1) {
            require_once 'Zend/Gdata/App/VersionException.php';
            throw new Zend_Gdata_App_VersionException('User activity feeds ' .
                'are not available in API version 1.');
        }

        $uri = null;
        if ($username instanceof Zend_Gdata_Query) {
            $uri = $username->getQueryUrl($this->getMajorProtocolVersion());
        } else {
            if (count(explode(',', $username)) >
                self::ACTIVITY_FEED_MAX_USERS) {
                require_once 'Zend/Gdata/App/InvalidArgumentException.php';
                throw new Zend_Gdata_App_InvalidArgumentException(
                    'Activity feed can only retrieve for activity for up to ' .
                    self::ACTIVITY_FEED_MAX_USERS .  ' users per request');
            }
            $uri = self::ACTIVITY_FEED_URI . '?author=' . $username;
        }

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