∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Preadditive C]
  [inst_2 : CategoryTheory.Balanced C] (S : CategoryTheory.ShortComplex C) (hS : S.Exact) (s : S.X₃ ⟶ S.X₂)
  (s_g : CategoryTheory.CategoryStruct.comp s S.g = CategoryTheory.CategoryStruct.id S.X₃)
  (hf : CategoryTheory.Mono S.f),
  CategoryTheory.CategoryStruct.comp S.f
      (hS.lift (CategoryTheory.CategoryStruct.id S.X₂ - CategoryTheory.CategoryStruct.comp S.g s) ⋯) =
    CategoryTheory.CategoryStruct.id S.X₁