∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Preadditive C]
  {S₁ S₂ : CategoryTheory.ShortComplex C} {φ₁ φ₂ φ₃ φ₄ : S₁ ⟶ S₂} (h : CategoryTheory.ShortComplex.Homotopy φ₁ φ₂)
  (h' : CategoryTheory.ShortComplex.Homotopy φ₃ φ₄),
  (φ₁ - φ₃).τ₃ = h.h₃ - h'.h₃ + CategoryTheory.CategoryStruct.comp (h.h₂ - h'.h₂) S₂.g + (φ₂ - φ₄).τ₃