∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {D : Type u₂} [inst_1 : CategoryTheory.Category.{v₂, u₂} D]
  {T : D} {S : CategoryTheory.Functor C D} {X Y : CategoryTheory.CostructuredArrow S T} (f g : X ⟶ Y),
  f.left = g.left → f = g