, but only that
    // which might be visible in the viewport.
    myDiagram = new go.Diagram('myDiagramDiv', {
      initialDocumentSpot: go.Spot.Center,
      initialViewportSpot: go.Spot.Center,

      // Use a virtualized TreeLayout which does not require
      // that the Nodes and Links exist first for an accurate layout
      layout: new VirtualizedTreeLayout({ angle: HORIZONTAL ? 0 : 90, nodeSpacing: 10 }),

      // Define the template for Nodes, used by virtualization.
      nodeTemplate: new go.N