proposition: Lemma msubset_neq0 A B : A `<=` B -> A != mset0 -> B != mset0.
proof: Proof. by rewrite -!mproper0 => sAB /mproper_sub_trans->. Qed.
imports: mathcomp(ssreflect ssrbool ssrnat eqtype ssrfun seq) mathcomp(choice path finset finfun fintype bigop tuple) finmap