∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] [inst_1 : CategoryTheory.Abelian C]
  {X Y : CategoryTheory.ShortComplex.SnakeInput C} (f : X.Hom Y),
  (CategoryTheory.ShortComplex.SnakeInput.Hom.id X).comp f = f