{C : Type u} →
  [inst : CategoryTheory.Category.{v, u} C] →
    [inst_1 : CategoryTheory.Preadditive C] →
      [inst_2 : CategoryTheory.Limits.HasZeroObject C] →
        {X : C} →
          {K : CochainComplex C ℤ} →
            {p q n : ℤ} →
              p + n = q →
                CochainComplex.HomComplex.Cochain K ((CochainComplex.singleFunctor C q).obj X) n ≃+ (K.X p ⟶ X)