以下代碼有什么問題？# Program to Show how to create a switch# import kivy moduleimport kivy# base Class of your App inherits from the App class.# app:always refers to the instance of your applicationfrom kivy.app import App# this restrict the kivy version i.e# below this kivy version you cannot# use the app or softwarekivy.require('1.9.0')# Builder is used when .kv file is# to be used in .py filefrom kivy.lang import Builder# The screen manager is a widget# dedicated to managing multiple screens for your application.from kivy.uix.screenmanager import ScreenManager, Screen# You can create your kv code in the Python fileBuilder.load_string(""" <ScreenOne>:     BoxLayout:         canvas.before:        Color:            rgba: (.4, .6, 9, 1)                          #(0,0,0,1)        Rectangle:            size: self.size            pos: self.pos        canvas:            Color:                rgba: (1, 1, 1,1)            RoundedRectangle:                size : self.width/2, self.height/3                pos : self.center_x - self.width/4 , self.center_y - self.height/6                                         radius: [(40, 40), (40, 40), (40, 40), (40, 40)]                       Button:             text: "Go to Screen 2"             background_color : 0, 0, 1, 1             on_press:                 # You can define the duration of the change                 # and the direction of the slide                 root.manager.transition.direction = 'left'                 root.manager.transition.duration = 1                 root.manager.current = 'screen_two' 我是 kivy 的新手，在網上獲得了這段代碼，效果很好。我現在試圖通過在其中放置一些畫布和形狀來更改它，但出現錯誤： AttributeError: 'kivy.graphics.context_instructions.Color' object has no attribute 'fbind'這是什么意思，我怎樣才能再次改變它以實現我的目標，即放置我的 2 個矩形并在它們上面放置按鈕？