如何使雷达图的工具提示在vue-chartjs中显示“标签”？

npm install vue-chartjs chart.js --save

import { Radar, mixins } from 'vue-chartjs';
const { reactiveProp } = mixins;

export default {
  extends: Radar,
  mixins: [reactiveProp],
  props: ['options'],
  mounted() {
    this.renderChart(this.chartData, this.options);
  }
}

<template>
  <div>
    <custom-radar :chart-data="chartData" :options="chartOptions"></custom-radar>
  </div>
</template>

data() {
  return {
    chartData: {
      labels: ['标签1', '标签2', '标签3', '标签4', '标签5'],
      datasets: [
        {
          label: '数据集1',
          backgroundColor: 'rgba(255, 99, 132, 0.2)',
          borderColor: 'rgba(255, 99, 132, 1)',
          pointBackgroundColor: 'rgba(255, 99, 132, 1)',
          pointBorderColor: '#fff',
          pointHoverBackgroundColor: '#fff',
          pointHoverBorderColor: 'rgba(255, 99, 132, 1)',
          data: [65, 59, 90, 81, 56]
        }
      ]
    },
    chartOptions: {
      tooltips: {
        callbacks: {
          label: function(tooltipItem, data) {
            return data.labels[tooltipItem.index] + ': ' + tooltipItem.yLabel;
          }
        }
      }
    }
  }
}