Element {
      static get is() { return 'tree-view'; }

      ready() {
        super.ready();
        this.$.tree.addEventListener('click', this.findElement.bind(this))
      }

      recomputeTree(parent, active) {
        this.$.tree.innerHTML = '';
        // Since we can't add a pojo to each button, generate a new index for
        // each button in the this.items array of useful data.
        this._index = 0;
        this.items = this.getChildren(parent, this.$.tree);
        this.highlight(active);
