proposition: Lemma card_dep_ffun : #|fT| = foldr muln 1 [seq #|rT x| | x : aT].
proof: Proof. by rewrite -card_family; apply/esym/eq_card=> f; apply/familyP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat seq choice) mathcomp(fintype tuple)