∀ (C : Type u_2) [inst : CategoryTheory.Category.{u_1, u_2} C] {X Y : CategoryTheory.Functor C C} (f : X ⟶ Y),
  CategoryTheory.CategoryStruct.comp (CategoryTheory.Functor.whiskerRight f (CategoryTheory.Functor.id C))
      Y.rightUnitor.hom =
    CategoryTheory.CategoryStruct.comp X.rightUnitor.hom f