proposition: Lemma remove_3 m x y e : MapsTo y e (remove x m) -> MapsTo y e m.
proof: Proof. rewrite <-!find_spec. apply remove_3bis. Qed.
imports: Coq(Bool Equalities Orders OrdersFacts OrdersLists) Coq(Morphisms Permutation SetoidPermutation) MMaps(Utils Comparisons Interface)