31   public func indexForKey(_ key: Key) -> Index? {  in indexForKey()
32     return storage.index(forKey: key)  in indexForKey()
35   public mutating func updateValue(_ value: Value, forKey key: Key) -> Value? {  in updateValue()
36     return storage.updateValue(value, forKey: key)  in updateValue()
39   public mutating func removeValueForKey(_ key: Key) -> Value? {  in removeValueForKey()
40     return storage.removeValue(forKey: key)  in removeValueForKey()
57   public subscript (key: Key) -> Value? {
59       return storage[key]
62       storage[key] = newValue
108     for (key, value) in elements {
109       storage[key] = value
144       let key = try Key.read(from: proto)  in read()  variable
146       map.storage[key] = value  in read()
155     for (key, value) in self.storage {  in write()
156       try Key.write(key, to: proto)  in write()