∀ {C : Type u_1} {inst : CategoryTheory.Category.{v_1, u_1} C} {inst_1 : CategoryTheory.Abelian C}
  {L : CochainComplex C ℤ} [self : L.IsKInjective] {K : CochainComplex C ℤ} (f : K ⟶ L),
  HomologicalComplex.Acyclic K → Nonempty (Homotopy f 0)