∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] {D : Type u_4}
  [inst_1 : CategoryTheory.Category.{u_3, u_4} D] (e : C ≌ D) (X : CategoryTheory.Arrow C),
  CategoryTheory.CategoryStruct.comp
      (e.functor.mapArrow.map (((CategoryTheory.Functor.mapArrowFunctor C C).mapIso e.unitIso).hom.app X))
      (((CategoryTheory.Functor.mapArrowFunctor D D).mapIso e.counitIso).hom.app (e.functor.mapArrow.obj X)) =
    CategoryTheory.CategoryStruct.id (e.functor.mapArrow.obj X)