             }
         }
         
-        var expired: Bool {
+        var isExpired: Bool {
             return estimatedExpiration.isPast
         }
     }

                    keys.remove(key)
                    continue
                }
                if object.estimatedExpiration.isPast {
                    storage.removeObject(forKey: nsKey)
                    keys.remove(key)
                }

            guard let object = storage.object(forKey: key as NSString) else {
                return nil
            }
            if object.isExpired {
                return nil
            }
            object.extendExpiration(extendingExpiration)
