如何在kivy carousel中显示多个项目？

from kivy.app import App
from kivy.uix.carousel import Carousel
from kivy.uix.carousel import CarouselItem

class MyCarousel(Carousel):
    def __init__(self, **kwargs):
        super(MyCarousel, self).__init__(**kwargs)
        self.size_hint = (0.8, 0.8)
        self.pos_hint = {'center_x': 0.5, 'center_y': 0.5}

class MyCarouselItem(CarouselItem):
    def __init__(self, **kwargs):
        super(MyCarouselItem, self).__init__(**kwargs)
        self.size_hint = (0.8, 0.8)
        self.pos_hint = {'center_x': 0.5, 'center_y': 0.5}

carousel = MyCarousel()
carousel.add_widget(MyCarouselItem())
carousel.add_widget(MyCarouselItem())
carousel.add_widget(MyCarouselItem())

class MyApp(App):
    def build(self):
        return carousel

if __name__ == '__main__':
    MyApp().run()