ndomColor(), // the node's color
        parent: i > 0 ? Math.floor((Math.random() * i) / 2) : undefined // the random parent's key
      };
      //!!!???@@@ this needs to be customized to account for your chosen Node template
      d.bounds = new go.Rect(0, 0, 70, 20);
      treedata.push(d);
    }
    myWholeModel.nodeDataArray = treedata;
    myDiagram.layoutDiagram(true);
  }

  // The following functions implement virtualization of the Diagram
  // Assume data.bounds is a Rect of the area occupied by 