∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Abelian C] {K L : CochainComplex C ℤ}
  {n : ℤ}
  [inst_2 :
    CategoryTheory.Localization.HasSmallLocalizedShiftedHom (HomologicalComplex.quasiIso C (ComplexShape.up ℤ)) ℤ K L]
  [inst_3 : K.IsKProjective]
  (b : CategoryTheory.Localization.SmallShiftedHom (HomologicalComplex.quasiIso C (ComplexShape.up ℤ)) K L n),
  CochainComplex.HomComplex.CohomologyClass.equivOfIsKProjective.symm b = Function.surjInv ⋯ b