∀ {C : Type u_1} [inst : CategoryTheory.Category.{u_4, u_1} C] {D : Type u_3}
  [inst_1 : CategoryTheory.Category.{u_2, u_3} D] [inst_2 : CategoryTheory.MonoidalCategory D]
  [inst_3 : CategoryTheory.SymmetricCategory D] (F G : CategoryTheory.Functor C D),
  CategoryTheory.CategoryStruct.comp (β_ F G).hom (β_ G F).hom =
    CategoryTheory.CategoryStruct.id (CategoryTheory.MonoidalCategoryStruct.tensorObj F G)