Section Properties.
Implicit Types x y : TVar.
Implicit Types xs ys : list TVar.
(* ---------------------------------------------------------------------- *)
(** **** Abstract properties of ok *)
(* ---------------------------------------------------------------------- *)
(** **** Properties of binds *)
(* ---------------------------------------------------------------------- *)
(** **** Properties of all_binds *)

(** All_Binds and remove. *)
Theorem all_binds_remove : forall A y (E F : gen_env A),
y ∉ E -> E ⊏ F ->
E ⊏ (F ∖ {y}).