protected function renderContentSets()
    {
        $ret = '';
        $ret .= $this->start('table');
        $ret .= $this->element('caption', 'Content Sets');
        foreach ($this->def->info_content_sets as $name => $lookup) {
            $ret .= $this->heavyHeader($name);
            $ret .= $this->start('tr');
            $ret .= $this->element('td', $this->listifyTagLookup($lookup));
            $ret .= $this->end('tr');
        }
        $ret .= $this->end('table');
        return $ret;
    }