{C : Type u} →
  [inst : CategoryTheory.Category.{v, u} C] →
    [inst_1 : CategoryTheory.Preadditive C] →
      {F G : CochainComplex C ℤ} →
        (φ₁ φ₂ : F ⟶ G) →
          Homotopy φ₁ φ₂ ≃
            { z //
              CochainComplex.HomComplex.Cochain.ofHom φ₁ =
                CochainComplex.HomComplex.δ (-1) 0 z + CochainComplex.HomComplex.Cochain.ofHom φ₂ }