proposition: Lemma eqb_sym x y : eqb x y = eqb y x.
proof: Proof. apply eq_bool_alt. rewrite !eqb_eq. split; apply K.eq_equiv. Qed.
imports: Coq(Bool Equalities Orders OrdersFacts OrdersLists) Coq(Morphisms Permutation SetoidPermutation) MMaps(Utils Comparisons Interface)