∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Preadditive C]
  {S₁ S₂ : CategoryTheory.ShortComplex C} (s : S₁.Splitting) (e : S₁ ≅ S₂),
  CategoryTheory.CategoryStruct.comp
      (CategoryTheory.CategoryStruct.comp e.inv.τ₃ (CategoryTheory.CategoryStruct.comp s.s e.hom.τ₂)) S₂.g =
    CategoryTheory.CategoryStruct.id S₂.X₃