         let cacheKey = cacheKeyForCellWithIdentifier(identifier, userInfo: userInfo)
         cachedHeights.removeValue(forKey: cacheKey)
     }
-
+    
     public func reset() {
         cachedHeights.removeAll(keepingCapacity: true)
         cacheKeysByArticleKey.removeAll(keepingCapacity: true)

    }
    
    public func invalidateArticleKey(_ articleKey: String?) {
        guard let articleKey = articleKey, let cacheKeys = cacheKeysByArticleKey[articleKey] else {
            return
        }
        for cacheKey in cacheKeys {
            cachedHeights.removeValue(forKey: cacheKey)
        }
        cacheKeysByArticleKey.removeValue(forKey: articleKey)
    }
    
    public func invalidateGroupKey(_ groupKey: String?) {

        }
        if let articleKey = articleKey {
            cacheKeysByArticleKey[articleKey, default: []].insert(cacheKey)
            if let groupKey = groupKey {
                groupKeysByArticleKey[articleKey, default: []].insert(groupKey)
            }
        }
        cachedHeights[cacheKey, default: [:]][columnWidth.roundedColumnWidth] = height
    }
