如何在Python中用Arcade制作的现有窗口上创建更新计时器？

import arcade
import time

class MyWindow(arcade.Window):
    def __init__(self, width, height):
        super().__init__(width, height, "My Window")
        self.start_time = time.time()
        self.elapsed_time = 0

    def on_draw(self):
        arcade.start_render()
        # 绘制其他窗口内容
        
        # 计算经过的时间
        self.elapsed_time = time.time() - self.start_time
        
        # 绘制计时器文本
        output = f"Elapsed Time: {self.elapsed_time:.2f} seconds"
        arcade.draw_text(output, 10, 10, arcade.color.WHITE, 14)

    def update(self, delta_time):
        # 更新其他窗口内容
        
        # 更新计时器
        self.elapsed_time = time.time() - self.start_time

def main():
    window = MyWindow(800, 600)
    arcade.run()

if __name__ == "__main__":
    main()