public function addFooter($type = PHPRtfLite_Container_Footer::TYPE_ALL, PHPRtfLite_Container_Footer $footer = null)
    {
        if ($footer === null) {
            $footer = new PHPRtfLite_Container_Footer($this, $type);
        }
        $this->_footers[$type] = $footer;

        return $footer;
    }