Section MonoidalCategoryLaws.
Context {E : Type -> Type}.
Local Open Scope cat.
Fact lift_case_sum {A B C} (ac : A -> C) (bc : B -> C) :
case_ (lift_ktree_ E _ _ ac) (lift_ktree bc)
⩯ lift_ktree (case__ Fun ac bc).
(** *** [Unitors] lemmas *)
(* This is probably generalizable into [Basics.Category]. *)

Lemma case_l_ktree' {A B: Type} (f: @ktree E (void + A) (void + B)) :
unit_l' >>> f ⩯ fun a => f (inr a).