proposition: Lemma enum_fsetE : enum_fset A = [seq val i | i <- enum fset_sub_type].
proof: Proof. by rewrite enumT unlock val_fset_sub_enum. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)