jump(cueTime, duration) {
    if (cueTime < 0 || cueTime > this.buffer.duration) {
      throw 'jump time out of range';
    }
    if (duration > this.buffer.duration - cueTime) {
      throw 'end time out of range';
    }

    var cTime = cueTime || 0;
    var dur = duration || undefined;
    if (this.isPlaying()) {
      this.stop(0);
      this.play(0, this.playbackRate, this.output.gain.value, cTime, dur);
    }
  }
Move the playhead of a soundfile that is currently playing to a
new position and a new duration, in seconds.
If none are given, will reset the file to play entire duration
from start to finish. To set the position of a soundfile that is
not currently playing, use the `play` or `loop` methods.

@method jump
@for p5.SoundFile
@param {Number} cueTime    cueTime of the soundFile in seconds.
@param {Number} duration    duration in seconds.