∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y Z : C} {f : X ⟶ Y} {g : X ⟶ Z}
  {t : CategoryTheory.Limits.PushoutCocone f g} (ht : CategoryTheory.Limits.IsColimit t) {W : C} (h : Y ⟶ W) (k : Z ⟶ W)
  (w : CategoryTheory.CategoryStruct.comp f h = CategoryTheory.CategoryStruct.comp g k),
  CategoryTheory.CategoryStruct.comp t.inr (CategoryTheory.Limits.PushoutCocone.IsColimit.desc ht h k w) = k