import { type Lens } from "https://deno.land/x/fun@v2.0.0-alpha.10/optics.ts";
Lens<S, A> is an alias of Optic<LensTag, S, A>. This means that the view
function of a Lens returns a pure A value. (s: S) => A. Some example lenses
are accessing the property of a struct, accessing the first value in a Pair,
and the trivial identity Lens. In general, a Lens is used for focusing on
exactly one value A contained in the value S.