∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] (P Q : C) [inst_1 : CategoryTheory.Limits.HasBinaryProduct P Q]
  [inst_2 : CategoryTheory.Limits.HasBinaryProduct Q P] {Z : C} (h : P ⨯ Q ⟶ Z),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.prod.braiding P Q).hom
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.prod.braiding Q P).hom h) =
    h