如何在echarts中添加渐变颜色？

I made a echart line graph https://stackblitz.com/edit/angular-aqghec?file=src%2Fapp%2Fapp.component.ts. Now, I want to add gradient color to it, as shown below:

In this link https://echarts.apache.org/en/option.html#series-line.areaStyle.color, it said it supports the setting as gradient color. But when I tried to do this as code given:

It gave this error:

该怎么办？

提前致谢。

  areaStyle: {
          color: new graphic.LinearGradient(0, 0, 0, 1, [
            {
              offset: 0,
              color: 'rgb(255, 158, 68)'
            },
            {
              offset: 1,
              color: 'rgb(255, 70, 131)'
            }])
        }

Echart有图形类，可以让你访问渐变属性。您可以根据需要对其进行微调，为数组中的颜色提供起点和终点。