   public override func collectionViewContentSize() -> CGSize {
     if self.collectionView?.superview == nil {
       return CGSize.zero
-        
     }
     
     var size = super.collectionViewContentSize()

  public var parallaxHeaderAlwaysOnTop: Bool = false
  public var disableStickyHeaders: Bool = false
  
  public func prepare() {
    prepare()
  }
  
  public override func initialLayoutAttributesForAppearingSupplementaryElementOfKind(elementKind: String, atIndexPath elementIndexPath: NSIndexPath) -> UICollectionViewLayoutAttributes? {
    
    let attributes = self.initialLayoutAttributesForAppearingSupplementaryElementOfKind(elementKind, atIndexPath: elementIndexPath as NSIndexPath)
    var frame = attributes?.frame
    frame!.origin.y += (self.parallaxHeaderReferenceSize?.height)!
    attributes?.frame = frame!

    
    origin.y = maxY
    
    attributes.frame = CGRect(x: origin.x, y: origin.y, width: attributes.frame.size.width, height: attributes.frame.size.width)
  }
}
