Slow Easing CollectionView and FlowLayout

BounceProofCollectionViewFlowLayout

import Foundation
import UIKit

class UIDirectionAbidingSlowingCollectionView : _UIDirectionAbidingCollectionView
{
    override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout)
    {
        super.init(frame: frame, collectionViewLayout: layout)
        let decelerationRate : CGFloat = 0.996
        setValue(NSValue(cgPoint: CGPoint(x: decelerationRate, y: decelerationRate)), forKey: "_" + "decelerationFactor")
        alwaysBounceVertical = true
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
}

public class BounceProofCollectionViewFlowLayout : UICollectionViewFlowLayout
{
    var lastVelocity : CGPoint = CGPoint.zero
    var enableEndBounce : Bool = false
    var invalidateOnScroll : Bool = false
    var lastProposedOffset : CGPoint = CGPoint.zero
   
    public override func invalidateLayout() {
        super.invalidateLayout()
       // print("BounceProofCollectionViewFlowLayout Invalidated Layout ")
    }
    override init()
    {
        super.init()
        self.minimumInteritemSpacing = 0.0
        self.minimumLineSpacing = 0.0
        self.sectionHeadersPinToVisibleBounds = true
        self.minimumInteritemSpacing = 0.0
        self.minimumLineSpacing = 0.0
        self.minimumInteritemSpacing = 0
        self.minimumLineSpacing = 0
        self.sectionInset = UIEdgeInsets.zero
        self.scrollDirection = .vertical
    }
    
    required public init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override public func shouldInvalidateLayout(forBoundsChange newBounds: CGRect) -> Bool
    {
        return invalidateOnScroll
    }
    
    override public func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {

        lastVelocity = velocity

        if scrollDirection == .vertical 
        {
            var _proposedContentOffset = proposedContentOffset
            
            if _proposedContentOffset.y < (1.0 - (self.collectionView?.contentInset.top ?? CGFloat(0.0)))
            {
                _proposedContentOffset.y = 1.0 - (self.collectionView?.contentInset.top ?? CGFloat(0.0))
            }   
            else if  _proposedContentOffset.y  >= self.collectionView!.contentSize.height - self.collectionView!.bounds.height + self.collectionView!.contentInset.bottom, enableEndBounce == false
            {
                _proposedContentOffset.y  = self.collectionView!.contentSize.height - self.collectionView!.bounds.height + self.collectionView!.contentInset.bottom - 1
            }
            
            lastProposedOffset = _proposedContentOffset
            
            return _proposedContentOffset
        }
        
        var _proposedContentOffset = proposedContentOffset
        
        if _proposedContentOffset.x < (1.0 - (self.collectionView?.contentInset.left ?? CGFloat(0.0)))
        {
            _proposedContentOffset.x = 1.0 - (self.collectionView?.contentInset.left ?? CGFloat(0.0))
        }
        else if _proposedContentOffset.x >= self.collectionView!.contentSize.width - self.collectionView!.bounds.width + self.collectionView!.contentInset.right, enableEndBounce == false
        {
             _proposedContentOffset.x = self.collectionView!.contentSize.width - self.collectionView!.bounds.width + self.collectionView!.contentInset.right - 1 - self.collectionView!.contentInset.left
        }
        
        lastProposedOffset = _proposedContentOffset
        return _proposedContentOffset
    }
}