∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] {X Y Z : C} (f : X ⟶ Y) (g : X ⟶ Z)
  [inst_1 : CategoryTheory.Limits.HasPushout f g] {Z_1 : C} (h : CategoryTheory.Limits.pushout g f ⟶ Z_1),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pushout.inl f g)
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pushoutSymmetry f g).hom h) =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.pushout.inr g f) h