mergeBy

inline fun <K, V1 : W, V2 : W, W> mergeBy(    map1: KoneMap<out K, V1>,     map2: KoneMap<out K, V2>,     keyEquality: Equality<K> = defaultEquality(),     keyHashing: Hashing<K>? = null,     keyOrder: Order<K>? = null,     resolve: (key: K, value1: V1, value2: V2) -> W): KoneMap<K, W>(source)