∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Preadditive C]
  {F G : CochainComplex C ℤ} (φ : F ⟶ G), CochainComplex.HomComplex.Cochain.ofHomotopy (Homotopy.refl φ) = 0