∀ {C : Type u₁} [inst : CategoryTheory.Category.{v₁, u₁} C] [inst_1 : CategoryTheory.MonoidalCategory C]
  (X : CategoryTheory.Center C) {Y₁ Y₂ : CategoryTheory.Center C} (f : Y₁ ⟶ Y₂) (U : C),
  CategoryTheory.CategoryStruct.comp
      (CategoryTheory.MonoidalCategoryStruct.whiskerRight (CategoryTheory.MonoidalCategoryStruct.whiskerLeft X.fst f.f)
        U)
      ((X.tensorObj Y₂).snd.β U).hom =
    CategoryTheory.CategoryStruct.comp ((X.tensorObj Y₁).snd.β U).hom
      (CategoryTheory.MonoidalCategoryStruct.whiskerLeft U
        (CategoryTheory.MonoidalCategoryStruct.whiskerLeft X.fst f.f))