∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {D : Type u₂} [inst_1 : CategoryTheory.Category.{v₂, u₂} D]
  (S : CategoryTheory.Functor C D) (T : D) (X : CategoryTheory.Comma S (CategoryTheory.Functor.fromPUnit T)),
  (CategoryTheory.CostructuredArrow.proj S T).obj X = X.left