A tree can be added into a sheet. To do so, there are two steps which must be done. First, the `value` attribute of the sheet must refer to a method, which return a tree instead of a list. Second, to display the tree, use the `<tc:columnNode/>` tag.

Tag Library Documentation: |

There is a tree in the first column. You can expand and collapse the items. The `<tc:columnNode/>` tag can contain several tags for a tree. In this example, it's a `<tc:treeIndent/>` to intent the single entries of the tree.

    <tc:sheet value="\#{sheetTreeController.solarTree}"
        var="solarObject" showRoot="true" showRootJunction="true">
      <tc:columnNode label="Name">
        <tc:treeIndent/>
        <tc:out value="\#{solarObject.userObject.name}"/>
        ...