Google Charts:禁用单击条形图时出现的条形图周围的黑色轮廓

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

function drawChart() {
  var data = google.visualization.arrayToDataTable([
    ['Year', 'Sales', 'Expenses'],
    ['2018', 1000, 400],
    ['2019', 1170, 460],
    ['2020', 660, 1120],
    ['2021', 1030, 540]
  ]);

  var options = {
    series: {
      0: { // 第一个系列的配置
        stroke: 'none' // 禁用边框
      },
      1: { // 第二个系列的配置
        stroke: 'none' // 禁用边框
      }
    }
  };

  var chart = new google.visualization.BarChart(document.getElementById('chart_div'));
  chart.draw(data, options);
}