Group by:
      <select onchange="groupBy(this.value)">
        <option value="section">Section</option>
        <option value="type">Type</option>
      </select>
    </div>
    <ul class="simple simple-toc" id="toc-list">
  <li><a class="reference" id="hello-worldcolon-my-name-is-nim-versionminus2minus0_toc" href="#hello-worldcolon-my-name-is-nim-versionminus2minus0">Hello world: my name is nim #version-2-0</a></li>
<ul class="simple"><li><a class="reference" id="hello-worldcolon-my-name-is-nim-versionmin