Matplotlib动画:当使用blit时，第一帧仍然在画布中

I'm trying to plot two rotating ellipses using the Matplotlib animation library, and I managed to get it working (more or less). The problem is that the first frame that is being rendered does not update, so while I got two rotating ellipses in my canvas, I also have the ellipses in their original position/orientation. Check out my simple piece of code:I'm trying to plot two rotating ellipses using