    // use a custom DraggingTool instead of the standard one, defined below
      draggingTool: new SnappingTool(),
      contextMenu: go.GraphObject.build('ContextMenu')
        .add(
          makeButton(
            'Paste',
            (e, obj) =>
              e.diagram.commandHandler.pasteSelection(
                e.diagram.toolManager.contextMenuTool.mouseDownPoint
              ),
            (o) =>
              o.diagram.commandHandler.canPasteSelection(
                o.diagram.toolManager.cont