Lemma MapFold_ext_f_1 : forall (m:Map A) (f g:ad -> A -> M) (pf:ad -> ad), (forall (a:ad) (y:A), MapGet _ m a = Some y -> f (pf a) y = g (pf a) y) -> MapFold1 _ _ neutral op f pf m = MapFold1 _ _ neutral op g pf m.