 }
 
 class CHTCollectionViewWaterfallLayout : UICollectionViewLayout{
-    let  CHTCollectionElementKindSectionHeader = "CHTCollectionElementKindSectionHeader"
+    let CHTCollectionElementKindSectionHeader = "CHTCollectionElementKindSectionHeader"
     let CHTCollectionElementKindSectionFooter = "CHTCollectionElementKindSectionFooter"
     
     var columnCount : NSInteger{

            
            let width = self.collectionView.frame.size.width - sectionInset.left - sectionInset.right
            let spaceColumCount = CGFloat(self.columnCount-1)
            let itemWidth = floor(width - (spaceColumCount*self.minimumColumnSpacing) / CGFloat(self.columnCount))
            
            /*
            * 2. Section header

        }
        let width:CGFloat = self.collectionView.frame.size.width - sectionInset.left-sectionInset.right
        let spaceColumCount:CGFloat = CGFloat(self.columnCount-1)
        return floor((width - (spaceColumCount*self.minimumColumnSpacing)) / CGFloat(self.columnCount))
    }
    
    override func prepareLayout(){
