How to add additional labels

This code draws a label at an arbitrary position in the chart.

var chart = new ac.ACLineChartBuilder()
    // ...
    .build();

var label = chart.createLabel();
label.setRotationAngle(45.0);
label.setXYWH(0.2, 0.2, 1.0, 1.0);
label.setStyle("TitleElement");
label.setText("TEST");
chart.addLabel(label);

chart.addToDom("chart");