addCue(time, callback, val) {
    var id = this._cueIDCounter++;

    var cue = new Cue(callback, time, id, val);
    this._cues.push(cue);

    // if (!this.elt.ontimeupdate) {
    //   this.elt.ontimeupdate = this._onTimeUpdate.bind(this);
    // }

    return id;
  }
Schedule events to trigger every time a MediaElement
 (audio/video) reaches a playback cue point.

 Accepts a callback function, a time (in seconds) at which to trigger
 the callback, and an optional parameter for the callback.


 @method  addCue
 @for p5.SoundFile
 @param {Number}   time     Time in seconds, relative to this media
                            element's playback. For example, to trigger
                            an event every time playback reaches two
                            seconds, pass in the number 2. This will be
                            passed as the first parameter to
                            the callback function.
 @param {Function} callback Name of a function that will be
                            called at the given time. The callback will
                            optionally receive the third argument as its
                            parameter.
 @param {Object} [value]    An object to be passed as the
                            optional parameter to the
                            callback function.
 @return {Number} id ID of this cue,
                     useful for removeCue(id)
 @example
 <div><code>
 let mySound;
 function preload() {
   mySound = loadSound('assets/Damscray_DancingTiger.mp3');
 }

 function setup() {
   let cnv = createCanvas(100, 100);
   cnv.mousePressed(canvasPressed);
   background(220);
   text('tap to play', 10, 20);

   // schedule calls to changeText
   mySound.addCue(0, changeText, "hello" );
   mySound.addCue(0.5, changeText, "hello," );
   mySound.addCue(1, changeText, "hello, p5!");
   mySound.addCue(1.5, changeText, "hello, p5!!");
   mySound.addCue(2, changeText, "hello, p5!!!!!");
 }

 function changeText(val) {
   background(220);
   text(val, 10, 20);
 }

 function canvasPressed() {
   mySound.play();
 }
 </code></div>