proposition: Lemma is_empty_spec' {elt}(m:t elt) : reflect (Empty m) (is_empty m).
proof: Proof. apply iff_reflect. apply is_empty_iff. Qed.
imports: Coq(Bool Equalities Orders OrdersFacts OrdersLists) Coq(Morphisms Permutation SetoidPermutation) MMaps(Utils Comparisons Interface)