∀ (C : Type u_2) [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.HasShift C ℤ]
  (T : CategoryTheory.Pretriangulated.Triangle C),
  CategoryTheory.CategoryStruct.comp ((CategoryTheory.Functor.id C).mapTriangle.obj T).mor₁
      (CategoryTheory.Iso.refl ((CategoryTheory.Functor.id C).mapTriangle.obj T).obj₂).hom =
    CategoryTheory.CategoryStruct.comp
      (CategoryTheory.Iso.refl ((CategoryTheory.Functor.id C).mapTriangle.obj T).obj₁).hom
      ((CategoryTheory.Functor.id (CategoryTheory.Pretriangulated.Triangle C)).obj T).mor₁