∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Abelian C]
  (S : CategoryTheory.ShortComplex.SnakeInput C),
  (CategoryTheory.ShortComplex.SnakeInput.Hom.id S).f₃ = CategoryTheory.CategoryStruct.id S.L₃