How to modify the tag graphic of the tooltip content item

const spec = { type: 'bar', data: [ { id: 'barData', values: [ { month: 'Monday', sales: 22 }, { month: 'Tuesday', sales: 13 }, { month: 'Wednesday', sales: 25 }, { month: 'Thursday', sales: 29 }, { month: 'Friday', sales: 38 } ] } ], tooltip: { mark: { content: [{ key: datum => datum['month'], value: datum => datum['sales'], shapeType: 'rect' }] } }, xField: 'month', yField: 'sales' }; const vchart = new VChart(spec, { dom: CONTAINER_ID }); vchart.renderSync();