import { type optics } from "https://deno.land/x/fun@v.2.0.0-alpha.11/mod.ts";
const { Fold } = optics;
Fold<S, A> is an alias of Optic<FoldTag, S, A>. This means that the view
function of a Fold returns a ReadonlyArray, (s: S) => ReadonlyArray<A>.
Some example Folds are accessing all of the values in a Record, Tree, Set,
etc. In general, a Fold is used for focusing on any number of values A
contained in the value S.