tupled method
If all items of this tuple are a Right, the respective items are turned into a tuple and returned as a Right. If any item is a Left, the first Left encountered is returned.
Implementation
Either<EE, (A, B, C, D, E, F, G, H, I, J, K, L, M, N, O)> tupled() =>
init().tupled().flatMap((x) => last.map((a) => x.append(a)));