∀ (C : Type u_1) (D : Type u_2) [inst : CategoryTheory.Category.{v_1, u_1} C]
  [inst_1 : CategoryTheory.MonoidalCategory C] [inst_2 : CategoryTheory.Category.{v_2, u_2} D]
  [inst_3 : CategoryTheory.MonoidalCategory.MonoidalRightAction C D] (x : Dᵒᵖ),
  CategoryTheory.MonoidalCategory.MonoidalRightActionStruct.actionUnitIso x =
    (CategoryTheory.MonoidalCategory.MonoidalRightActionStruct.actionUnitIso (Opposite.unop x)).symm.op