This example uses the treePropertyOverride tag to override the action. By default, the action set on the
root of the tree is used for both expansion and selection. In addition, a treeItem may set it's own action
that will be called for selection on that element. The treePropertyOverride tag is used to apply new images and actions to the
subtree. In this example, we override the selection action which is visible in the Tree Postback Information. The
labels of the node reflect the expected action to be called on selection.