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