∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.CartesianMonoidalCategory C]
  (X Y Z : C),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.MonoidalCategoryStruct.associator X Y Z).inv
      (CategoryTheory.SemiCartesianMonoidalCategory.snd (CategoryTheory.MonoidalCategoryStruct.tensorObj X Y) Z) =
    CategoryTheory.CategoryStruct.comp
      (CategoryTheory.SemiCartesianMonoidalCategory.snd X (CategoryTheory.MonoidalCategoryStruct.tensorObj Y Z))
      (CategoryTheory.SemiCartesianMonoidalCategory.snd Y Z)