public function addGenerator()
    {
        if ($this->version == Feed::ATOM)
            $this->setChannelElement('atom:generator', 'FeedWriter', array('uri' => 'https://github.com/mibe/FeedWriter'));
        else if ($this->version == Feed::RSS2)
            $this->setChannelElement('generator', 'FeedWriter');
        else
            throw new InvalidOperationException('The generator element is not supported in RSS1 feeds.');

        return $this;
    }