如何操作Chart.js饼图的特定工具提示值？

<canvas id="myChart"></canvas>

var data = {
  labels: ['标签1', '标签2', '标签3'],
  datasets: [{
    data: [10, 20, 30]
  }]
};

var ctx = document.getElementById('myChart').getContext('2d');
var myChart = new Chart(ctx, {
  type: 'pie',
  data: data
});

var myChart = new Chart(ctx, {
  type: 'pie',
  data: data,
  options: {
    tooltips: {
      callbacks: {
        label: function(tooltipItem, data) {
          var dataset = data.datasets[tooltipItem.datasetIndex];
          var value = dataset.data[tooltipItem.index];
          return value + ' 占比：' + (value / dataset.data.reduce((a, b) => a + b, 0) * 100).toFixed(2) + '%';
        }
      }
    }
  }
});