如何为这个dygraph添加注释？

Question

有谁熟悉javascript dygraph库？我想为这个dygraph添加一个注释，但它看起来与在线教程中的内容完全不同。

g = new Dygraph(
document.getElementById("visualization"),
chart_data, {
    labelsDiv: document.getElementById('status'),
    labelsSeparateLines: false,
    labelsKMB: true,
    labels: ["X", "Val"],
    legend: 'onmouseover',
    colors: ["rgb(88,143,235)"],
    width: 640,
    height: 480,
    //title: '<?  ?>',
    //xlabel: '<?= $xAxisLabel ?>',
    //ylabel: '<?= $yAxisLabel ?>',
    axisLineColor: 'white',
    //valueRange: <?= $yAxisRangeStr ?>,
    showRangeSelector: true,
    dateWindow: [(d.getTime() - 2 * 7 * 24 * 60 * 60 * 1000), d.getTime()],
    underlayCallback: function (ctx, area, dygraph) {
        ctx.strokeStyle = 'black';
        ctx.strokeRect(area.x, area.y, area.w, area.h);
    }
    // echo($chart["dygraphs-scaling"]) ?>
    // drawXGrid: false
});