∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] {X Y Z W : Cᵒᵖ} {f : X ⟶ Y} {g : Z ⟶ W}
  (h : CategoryTheory.RetractArrow f g),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Arrow.Hom.right h.r).unop (CategoryTheory.Arrow.mk g.unop).hom =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.Arrow.mk f.unop).hom (CategoryTheory.Arrow.Hom.left h.r).unop