∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.HasShift C ℤ]
  {X Y Z : CategoryTheory.Pretriangulated.Triangle C} (f : X ⟶ Y) (g : Y ⟶ Z),
  (CategoryTheory.CategoryStruct.comp f g).hom₁ = CategoryTheory.CategoryStruct.comp f.hom₁ g.hom₁