"A function that returns the result of applying the given [[function|resulting]] to the [[key|Entry.key]] of a given [[Entry]], discarding its `item`. Map<String,List<Item>> map = ... ; {String*} uppercaseKeys = map.map(forKey(String.uppercased));" see (`function forItem`) tagged("Functions") shared Result forKey<Key,Result>(Result resulting(Key key)) (Key->Anything entry) given Key satisfies Object => resulting(entry.key);