工具提示在Google散点图中不起作用

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

function drawChart() {

  var data = new google.visualization.DataTable();

  data.addColumn('string', 'Year');
  data.addColumn('number', 'Sales');
  // A column for custom tooltip content
  data.addColumn({
    type: 'string',
    role: 'tooltip',
  });

  data.addRows([
    ['Name1', 1000, 'Tooltip string'],
    ['Name2', 1170, 'Tooltip string'],
    ['Name3', 660, 'Tooltip string'],
  ]);

  var options = {
    width: 800,
    height: 500,
    chart: {
      title: 'Example',
    },
  };

  var chart = new google.visualization.ScatterChart(document.getElementById('scatterchart_material'));

  chart.draw(data, options);
}

<script src="https://www.gstatic.com/charts/loader.js"></script>
<div id="scatterchart_material"></div>