∀ {C : Type u} [inst : CategoryTheory.Category.{v, u} C] [inst_1 : CategoryTheory.MonoidalCategory C] {X Y : C}
  (f : X ⟶ Y),
  CategoryTheory.MonoidalCategoryStruct.whiskerLeft (CategoryTheory.MonoidalCategoryStruct.tensorUnit C) f =
    CategoryTheory.CategoryStruct.comp (CategoryTheory.MonoidalCategoryStruct.leftUnitor X).hom
      (CategoryTheory.CategoryStruct.comp f (CategoryTheory.MonoidalCategoryStruct.leftUnitor Y).inv)