有没有办法用PyGtk制作一个不确定的复选按钮？

import gi
gi.require_version('Gtk', '3.0')
from gi.repository import Gtk

def on_button_toggled(button):
    if button.get_active():
        state = "确定"
    else:
        state = "不确定"
    print("复选按钮状态:", state)

win = Gtk.Window()
win.connect("destroy", Gtk.main_quit)

button = Gtk.CheckButton.new_with_label("不确定复选按钮")
button.connect("toggled", on_button_toggled)
button.set_active(None)

win.add(button)
win.show_all()

Gtk.main()