如何在Google Chart上添加自定义工具提示？

google.charts.load('current', {packages: ['corechart']});
google.charts.setOnLoadCallback(drawChart);

function drawChart() {
  var data = google.visualization.arrayToDataTable([
    ['Year', 'Sales', 'Expenses'],
    ['2016', 1000, 400],
    ['2017', 1170, 460],
    ['2018', 660, 1120],
    ['2019', 1030, 540]
  ]);

  var chartWrapper = new google.visualization.ChartWrapper({
    chartType: 'ColumnChart',
    dataTable: data,
    options: {
      title: 'Sales and Expenses',
      width: 600,
      height: 400
    }
  });

  var chart = chartWrapper.getChart();

  google.visualization.events.addListener(chart, 'onmouseover', function(e) {
    var selection = chart.getSelection();
    if (selection.length > 0) {
      var row = selection[0].row;
      var column = selection[0].column;
      var value = data.getValue(row, column);

      var tooltip = document.createElement('div');
      tooltip.innerHTML = 'Value: ' + value;
      tooltip.style.position = 'absolute';
      tooltip.style.left = e.pageX + 'px';
      tooltip.style.top = e.pageY + 'px';
      tooltip.style.backgroundColor = 'white';
      tooltip.style.border = '1px solid black';
      tooltip.style.padding = '5px';

      chart.getContainer().appendChild(tooltip);
    }
  });

  chartWrapper.draw(document.getElementById('chart_div'));
}