Definition normalize {X} `{Finite X} (d : dist X) : dist X.
refine {|
dist_pmf := map (fun x => (x, eval_dist d (Classes.eqb x))) enum;
dist_law := _;
|}.

Lemma vertical_strip {X Y} `{Finite X, Finite Y} (x : X):
count (fun p => Classes.eqb x (fst p)) = card Y.