Consecutive animation in TornadoFX?

After reading through the documentation, I'm still a bit confused on how to execute an animation after another one has completed. I have a timeline like so:

timeline {
  keyframe(Duration.seconds(0.5)) {
    keyvalue(firstImg.scaleXProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(firstImg.scaleYProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(firstImg.rotateProperty(), 0.0, interpolator = Interpolator.EASE_BOTH)
  }

  keyframe(Duration.seconds(0.5)) {
    keyvalue(secondImg.scaleXProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(secondImg.scaleYProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(secondImg.rotateProperty(), 0.0, interpolator = Interpolator.EASE_BOTH)
  }

  keyframe(Duration.seconds(0.5)) {
    keyvalue(thirdImg.scaleXProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(thirdImg.scaleYProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(thirdImg.rotateProperty(), 0.0, interpolator = Interpolator.EASE_BOTH)
  }

  keyframe(Duration.seconds(0.5)) {
    keyvalue(fourthImg.scaleXProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(fourthImg.scaleYProperty(), 1.0, interpolator = Interpolator.EASE_BOTH)
    keyvalue(fourthImg.rotateProperty(), 0.0, interpolator = Interpolator.EASE_BOTH)
  }
}

This runs them all at once, but I would like to run each animation after the other one has finished! I can't quite figure out how to do this.. (sorry if this is obvious, I am very new to Kotlin and Java in general!)

I see that the keyframe has an onFinished property but I can't quite figure out what I'm supposed to actually set it to. Is there a better way to do this? Thank you!