      v.alignment = go.TreeAlignment.Bus; // this is required
        v.nodeSpacing = 50; // control the distance of the assistants from the parent's main links
      } else if (v.node == null && v.childrenCount > 0) {
        // found the substitute parent for non-assistant children
        //v.alignment = go.TreeAlignment.CenterChildren;
        //v.breadthLimit = 3000;
        v.layerSpacing = 0;
      }
    }

    commitLinks() {
      super.commitLinks();
      // make sure the middle segment of an ort