[cleue]

Unfortunately there is no way to use variadic arguments in a type safe way in go (yet) - except for the special case that all arguments are of the same type.

This is why some of the functions that work with many arguments (such as `Pipe`, `Flow`, `Traverse` ...) carry their cardinality as a suffix. Their shapes are then auto-generated up to a max cardinality that seems to make sense in practice.

So the traverse tuple function does not only exist for cardinality 2 but also for higher ones. But unfortunately you have to specify it explicitly.