我想有机会在builder中更改或删除矩形，但是出现AttributeError。 我该如何解决？我希望你能帮助我

from kivy.app import App
from kivy.uix.floatlayout import FloatLayout
from kivy.uix.image import Image
from kivy.lang import Builder
from kivy.core.window import Window
from kivy.graphics import Color,Rectangle
Builder.load_string('''
<RootWidget>
    FloatLayout:
        id: layout
        canvas.before:
            Rectangle:
                id: image
                size: (100,180)
                pos: (223,191)
                source:'image.gif'
''')
class RootWidget(FloatLayout):
    def __init__(self,**kwargs):
        super(RootWidget,self).__init__(**kwargs)
        self.ids.layout.remove_widget(self.ids.image)

class WindowApp(App):
    def build(self):
        return RootWidget()

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