∀ {C : Type u_2} [inst : CategoryTheory.Category.{u_1, u_2} C] (T : CategoryTheory.Monad C) {X Y Z : C} (f : X ⟶ Y)
  (g : Y ⟶ Z),
  { of := CategoryTheory.CategoryStruct.comp (CategoryTheory.CategoryStruct.comp f g) (T.η.app Z) } =
    CategoryTheory.CategoryStruct.comp { of := CategoryTheory.CategoryStruct.comp f (T.η.app Y) }
      { of := CategoryTheory.CategoryStruct.comp g (T.η.app Z) }