∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Limits.HasZeroObject C]
  [inst_2 : CategoryTheory.HasShift C ℤ] [inst_3 : CategoryTheory.Preadditive C]
  [inst_4 : ∀ (n : ℤ), (CategoryTheory.shiftFunctor C n).Additive] [hC : CategoryTheory.Pretriangulated C]
  (T₁ T₂ : CategoryTheory.Pretriangulated.Triangle C) (hT₁ : T₁ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles)
  (hT₂ : T₂ ∈ CategoryTheory.Pretriangulated.distinguishedTriangles) (a : T₁.obj₁ ⟶ T₂.obj₁) (b : T₁.obj₂ ⟶ T₂.obj₂)
  (comm : CategoryTheory.CategoryStruct.comp T₁.mor₁ b = CategoryTheory.CategoryStruct.comp a T₂.mor₁),
  (CategoryTheory.Pretriangulated.completeDistinguishedTriangleMorphism T₁ T₂ hT₁ hT₂ a b comm).hom₁ = a