∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.Limits.HasBinaryCoproducts C]
  (W X Y Z : C),
  CategoryTheory.CategoryStruct.comp
      (CategoryTheory.Limits.coprod.map (CategoryTheory.Limits.coprod.associator W X Y).hom
        (CategoryTheory.CategoryStruct.id Z))
      (CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.coprod.associator W (X ⨿ Y) Z).hom
        (CategoryTheory.Limits.coprod.map (CategoryTheory.CategoryStruct.id W)
          (CategoryTheory.Limits.coprod.associator X Y Z).hom)) =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.Limits.coprod.associator (W ⨿ X) Y Z).hom
      (CategoryTheory.Limits.coprod.associator W X (Y ⨿ Z)).hom