∀ (C : Type u₁) [inst : CategoryTheory.Category.{v₁, u₁} C] [inst_1 : CategoryTheory.MonoidalCategory C],
  CategoryTheory.Functor.OplaxMonoidal.η (CategoryTheory.Center.forget C) =
    CategoryTheory.CategoryStruct.id
      ((CategoryTheory.Center.forget C).obj
        (CategoryTheory.MonoidalCategoryStruct.tensorUnit (CategoryTheory.Center C)))