在Chart.js中这些线框是什么，我如何关闭它们？

var chartOptions = {
  scales: {
    xAxes: [{
      gridLines: {
        display: false
      },
      ticks: {
        display: false
      }
    }],
    yAxes: [{
      gridLines: {
        display: false
      },
      ticks: {
        display: false
      }
    }]
  }
};

var chartData = {
  // 图表数据
};

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