proposition: Lemma 𝔹_Bool_subtype : forall b, 𝔹 b ⊆ Bool.
proof: Proof. unfold 𝔹, Bool. intro b. apply sub_Forall_add. intro Z. intros π Hπ. now exists (fun _ => Z). Qed.
imports: Setoid Arith.Peano_dec ClassicalRealizability.Kbase