∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] {X Y Z : C} {f f' : X ⟶ Y} {g : Y ⟶ Z}
  (H : CategoryTheory.IsPushout f f' g g) (s : CategoryTheory.Limits.Cofork f f')
  (m : (CategoryTheory.Limits.Cofork.ofπ g ⋯).pt ⟶ s.pt),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.Cofork.ofπ g ⋯).π m = s.π →
    m = H.isColimit.desc (CategoryTheory.Limits.PushoutCocone.mk s.π s.π ⋯)