   var threshold: CGFloat = 0.1
   var stiffness: CGPoint = CGPoint(x: 50, y: 50)
 
-  var initiallyOutOfBound = false
   func animateDone() {
     guard let scrollView = scrollView else { return }
     targetOffsetX = nil

  func animateToTargetOffset(_ target: CGPoint, stiffness: CGFloat = 1000, damping: CGFloat = 30) {
    targetOffsetY = target.y
    targetOffsetX = target.x
    // default value
    self.stiffness = CGPoint(x: stiffness, y: stiffness)
    self.damping = CGPoint(x: damping, y: damping)


  override func didEnd(finished: Bool) {
    super.didEnd(finished: finished)
    scrollView?.didEndScroll()
  }

