proposition: Lemma demo_multiset_union_permut_simpl_1 : forall l1 l2 l3 : multiset A, (l1 \u l2 \u l3) = (l3 \u l2 \u l1).
proof: Proof. Proof using. intros. permut_simpl_prepare. permut_simpl_once. permut_simpl_once. permut_simpl_once. rew_permut_simpl. permut_conclude. Qed.
imports: TLC(LibTactics LibLogic LibReflect LibRelation LibList LibInt LibNat LibOperation LibEpsilon LibSet LibMonoid)