f to the elements of this list in the applicative functor defined by
Folds this list using a function that operates on the homogeneous type of the elements of this list.
Discards the heterogeneous type information and constructs a plain List from this KList's elements.
Apply the natural transformation
f to each element.
transform(f) . apply(x => x), this is the essence of the iterator at the level of natural transformations.