<al-lookup name="indent">
 <al-item expr="0">  </al-item>
 <al-item expr="1"> |</al-item>
 <al-item expr="2"> \</al-item>
</al-lookup>
<al-tree iter="n" expr="tree">
 <al-for iter="c" expr="range(n.depth())">
  <al-value expr="n.line(c.value())" lookup="indent">
 </al-for>
 -<al-value expr="n.value().name" whitespace="newline">
</al-tree>
