∀ {I : Type u_1} {J : Type u_2} (e : I ≃ J) (X : CategoryTheory.Discrete I),
  CategoryTheory.CategoryStruct.comp
      ((CategoryTheory.Discrete.functor (CategoryTheory.Discrete.mk ∘ ⇑e)).map
        ((CategoryTheory.Discrete.natIso fun i => CategoryTheory.eqToIso ⋯).hom.app X))
      ((CategoryTheory.Discrete.natIso fun j => CategoryTheory.eqToIso ⋯).hom.app
        ((CategoryTheory.Discrete.functor (CategoryTheory.Discrete.mk ∘ ⇑e)).obj X)) =
    CategoryTheory.CategoryStruct.id ((CategoryTheory.Discrete.functor (CategoryTheory.Discrete.mk ∘ ⇑e)).obj X)