proposition: Lemma mem_fset_sub_enum x : x \in fset_sub_enum.
proof: Proof. by rewrite mem_undup mem_pmap -valK map_f // fsvalP. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)