∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.MonoidalCategory C] (X : C)
  {Y₁ Y₂ : C} (f : Y₁ ⟶ Y₂),
  CategoryTheory.MonoidalCategoryStruct.whiskerLeft X f =
    CategoryTheory.MonoidalCategoryStruct.tensorHom (CategoryTheory.CategoryStruct.id X) f