removeCue(id) {
    var cueLength = this._cues.length;
    for (var i = 0; i < cueLength; i++) {
      var cue = this._cues[i];
      if (cue.id === id) {
        this._cues.splice(i, 1);
        break;
      }
    }

    if (this._cues.length === 0) {
      // TO DO: remove callback
      // this.elt.ontimeupdate = null
    }
  }
Remove a callback based on its ID. The ID is returned by the
 addCue method.

 @method removeCue
 @for p5.SoundFile
 @param  {Number} id ID of the cue, as returned by addCue