plt.pause uses removed `start_event_loop_default` API

As the title suggests, attempting to pause through matplotlib currently raises an error. The minimum working example is:

%matplotlib widget
from matplotlib import pyplot as plt

plt.plot([1,2,3])
plt.pause(1)    
plt.plot([3,2,1])
plt.close()

This raises an attribute error trying to call FigureCanvasBase.start_event_loop_default. A little googling suggests this function has been removed since version 3.0.

Taking inspiration from #17, I guess the simplest get around is using time.sleep but is there a better solution?

Thanks for your help.

从提供的 Jupyter 示例开始，跟踪 plt.pause 到报告中提到的入口点 FigureCanvasBase.start_event_loop_default，并使用 issue #17 了解相关上下文。完成的标准是：示例运行时不再出现由已移除 API 导致的 AttributeError，并且两个绘图都能按描述显示和关闭。