∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {X Y Z : C} (f : X ⟶ Z) (g : X ⟶ Y)
  [inst_1 : CategoryTheory.Limits.HasPushout f g] [inst_2 : CategoryTheory.Limits.HasPullback f.op g.op] {Z_1 : C}
  (h : Opposite.unop (CategoryTheory.Limits.pullback f.op g.op) ⟶ Z_1),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pushout.inr f g)
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pushoutIsoUnopPullback f g).hom h) =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pullback.snd f.op g.op).unop h