Example
An option item of a tree. This is an element within a tree that may be expanded or collapsed if it contains a sub-level group of treeitems.
<ul role="tree">
<li role="treeitem">
Part 1
<ul>
<li role="treeitem">Chapter 1</li>
<li role="treeitem">Chapter 2</li>
<li role="treeitem">Chapter 3</li>
</ul>
</li>
<li role="treeitem">
Part 2
<ul>
<li role="treeitem">Chapter 4</li>
<li role="treeitem">Chapter 5</li>
<li role="treeitem">Chapter 6</li>
</ul>
</li>
<li role="treeitem">
Part 3
<ul>
<li role="treeitem">Chapter 7</li>
<li role="treeitem">Chapter 8</li>
<li role="treeitem">Chapter 9</li>
</ul>
</li>
</ul>
