proposition: Lemma foreach_single : forall P X, P X -> @foreach A (multiset A) _ P (\{ X }).
proof: Proof. Proof using. intros_all. rewrite in_single_eq in H0. subst*. Qed.
imports: TLC(LibTactics LibLogic LibReflect LibRelation LibList LibInt LibNat LibOperation LibEpsilon LibSet LibMonoid)