Notation "a =jm b" := (jmeq id a b) (at level 50).

(* Specifications: *)
Lemma contV B (P : B -> B -> Prop) : (forall x x', x =jm x' -> P x x') <-> forall x, P x x.
Lemma contVT B (P : B -> B -> Prop) : (forall x x', B = B -> x =jm x' -> P x x') <-> forall x, P x x.