如何在chartjs中显示两条重叠线

<script src="https://cdn.jsdelivr.net/npm/chart.js"></script>

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

var ctx = document.getElementById('myChart').getContext('2d');

var data = {
  labels: ['January', 'February', 'March', 'April', 'May', 'June', 'July'],
  datasets: [{
    label: 'Dataset 1',
    data: [10, 20, 30, 40, 50, 60, 70],
    borderColor: 'red',
    backgroundColor: 'transparent',
    yAxisID: 'y-axis-1'
  }, {
    label: 'Dataset 2',
    data: [5, 15, 25, 35, 45, 55, 65],
    borderColor: 'blue',
    backgroundColor: 'transparent',
    yAxisID: 'y-axis-1'
  }]
};

var myChart = new Chart(ctx, {
  type: 'line',
  data: data,
  options: {
    scales: {
      yAxes: [{
        id: 'y-axis-1',
        type: 'linear',
        position: 'left',
      }]
    }
  }
});