∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] {X Y Z : Cᵒᵖ} (f : X ⟶ Z) (g : Y ⟶ Z)
  [inst_1 : CategoryTheory.Limits.HasPullback f g],
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pushout.inr f.unop g.unop)
      (CategoryTheory.Limits.pullbackIsoOpPushout f g).hom.unop =
    (CategoryTheory.Limits.pullback.snd f g).unop