     }()
 
     func scrollViewDidScroll(_ scrollView: UIScrollView) {
-        print(scrollView.value(forKey: "_verticalVelocity"))
         decelerator.invalidateIfNeeded()
     }
 }

}

final class NestedScrollViewVC: UIViewController {
    private lazy var outerScrollView: UIScrollView = {
        let outer = UIScrollView()
        outer.delegate = self
        outer.backgroundColor = .systemRed
        return outer
    }()
    
    private lazy var nestedUIScrollView: UIScrollView = {
        let nested = UIScrollView()
        nested.delegate = self
        nested.backgroundColor = .systemBlue
        return nested
    }()

        view.backgroundColor = .white
        
        view.addSubview(outerScrollView)
        outerScrollView.contentSize = CGSize(width: view.frame.width - 20, height: view.frame.height * 1.1)
        outerScrollView.frame = CGRect(x: 10, y: 50, width: view.frame.width - 20, height: view.frame.height - 88)
        
        outerScrollView.addSubview(nestedScrollView)
        outerScrollView.nested = nestedScrollView
        nestedScrollView.contentSize = CGSize(width: view.frame.width - 40, height: 5000)
        nestedScrollView.frame = CGRect(x: 10, y: 320, width: view.frame.width - 40, height: view.frame.height)
    }
}


final class OuterScrollView: UIScrollView, UIScrollViewDelegate {
    var outerDeceleration: ScrollingDeceleration?
