proposition: Lemma fsubset_neq0 A B : A `<=` B -> A != fset0 -> B != fset0.
proof: Proof. by rewrite -!fproper0 => sAB /fproper_sub_trans->. Qed.
imports: HB(structures) mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop)