gram.lastInput;
      var currobj = e.targetObject;
      if (currobj !== null && (currobj.name === 'ButtonA' || (currobj.panel !== null && currobj.panel.name === 'ButtonA'))) {
        str = data.aToolTip;
      } else {
        str = data.bToolTip;
      }
      return str;
    }

    // define tooltips for buttons
    var tooltipTemplate = go.GraphObject.build('ToolTip', { 'Border.fill': 'whitesmoke', 'Border.stroke': 'lightgray' })
      .add(
        new go.TextBlock({
          font: '8pt Roboto, sans