Using angular-ui-tree add a child node to the clicked node

I'm using "angular-ui-tree": "^2.22.5"

<div ui-tree-handle 
    class="tree-node ctg-tree-node-content ng-scope angular-ui-tree-handle" 
    ng-click="ctrl.selectPage(this)">

In the controller for this component

public selectPage(item: any) {
    console.log('depth of selected node: ' + item.depth());
    item.$nodeScope.insertNode(0, {
        name: 'dummy new child node'
    });
}

This adds a new node into the tree, but its a sibling to the selected node .. how can I add my new node as a child of the selected node?

The clicked node, may or may not have any children already.