AmCharts 4-如何在使用API时设置导出的名称?

this.config = {};
this.chartId = 'myId';
this.chartType = am4charts.PieChart;

this.chart = am4core.createFromConfig(
  {
    this.config,
    this.chartId,
    this.chartType
  }
);

然后做:

this.chart.exporting.export('png');

导出文件的名称默认设置为“amCharts.png". 如何将名称设置为其他名称?

this.config = { export: { fileName: 'yay' } };
this.config = { fileName: 'yay' };