- * Get the internal dataset index given its name. These are numbered starting from 0,
- * and only count visible sets.
- * @private
+ * Trigger a callback when the dygraph has drawn itself and is ready to be
+ * manipulated. This is primarily useful when dygraphs has to do an XHR for the
+ * data (i.e. a URL is passed as the data source) and the chart is drawn
+ * asynchronously. If the chart has already drawn, the callback will fire
+ * immediately.
+ *
+ * This is a good place to call setAnnotation().
+ *
+ * @param {function(!Dygraph)} callback The callback to trigger when the chart
+ * is ready.