∀ {C : Type u_4} [inst : CategoryTheory.Category.{u_3, u_4} C] [inst_1 : CategoryTheory.MonoidalCategory C]
  {D : Type u_2} [inst_2 : CategoryTheory.Category.{u_1, u_2} D]
  [inst_3 : CategoryTheory.MonoidalCategory.MonoidalLeftAction C D] (X : D),
  CategoryTheory.CategoryStruct.comp
      (CategoryTheory.MonoidalCategory.MonoidalLeftActionStruct.actionHomLeft CategoryTheory.MonObj.one X)
      (CategoryTheory.MonoidalCategory.MonoidalLeftActionStruct.actionUnitIso X).hom =
    (CategoryTheory.MonoidalCategory.MonoidalLeftActionStruct.actionUnitIso X).hom