∀ {C : Type u_1} [inst : CategoryTheory.Category.{v_1, u_1} C] [inst_1 : CategoryTheory.Abelian C]
  {X Y : CategoryTheory.ShortComplex.SnakeInput C} (f : X ⟶ Y),
  (CategoryTheory.ShortComplex.SnakeInput.functorL₂'.map f).τ₂ = f.f₃.τ₁