如何在kivy中让绘制的线条每隔x秒消失一次？

from kivy.app import App
from kivy.uix.widget import Widget
from kivy.graphics import Line
from kivy.clock import Clock

class LineWidget(Widget):
    def __init__(self, **kwargs):
        super(LineWidget, self).__init__(**kwargs)
        self.line = None

    def draw_line(self):
        with self.canvas:
            self.line = Line(points=[100, 100, 400, 400], width=2)

    def clear_line(self):
        self.canvas.clear()

class MyApp(App):
    def build(self):
        line_widget = LineWidget()
        line_widget.draw_line()
        Clock.schedule_interval(line_widget.clear_line, x)
        return line_widget

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