 during mouse-over
        new go.Shape({ isPanelMain: true, strokeWidth: 6, stroke: 'transparent' })
          .bindObject('stroke', 'isHighlighted', (h) => (h ? 'red' : 'transparent')),
        new go.Shape({ isPanelMain: true, strokeWidth: 1 }),
        new go.Shape({ toArrow: 'Standard' })
      );

    // Decide whether a link from node1 to node2 may be created by a drop operation
    function mayConnect(node1, node2) {
      return node1 !== node2;
    }

    // Modify the CommandHandler's doKeyDown t