Gradient fill for line type chart about amcharts5 HOT 1 OPEN

  var series;
  switch (seriesType) {
    case "line":
    	delete newSettings.openValueYField;
      series = mainPanel.series.push(am5xy.LineSeries.new(root, newSettings));
      series.fills.template.setAll({
        visible: true,
        fillOpacity: 0.2
      });   
      break;
    case "candlestick":
    case "procandlestick":
      newSettings.clustered = false;
      newSettings.openValueYField = "Open";
      series = mainPanel.series.push(am5xy.CandlestickSeries.new(root, newSettings));
      if (seriesType == "procandlestick") {
        series.columns.template.get("themeTags").push("pro");
      }
      break;
    case "ohlc":
      newSettings.clustered = false;
      newSettings.openValueYField = "Open";
			series = mainPanel.series.push(am5xy.OHLCSeries.new(root, newSettings));
      break;
  }