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