How to remove an element in Pycairo?

Question

Python

Hello. I am trying to make a simple drawing program. I can draw a rectangle based on the mouse coordinates, but I don't know how to remove the old elements so that I have the behavior like in the second video. How can I implement the behavior from the second video (Where is the rectangle on the white background) ?
Now like this: https://youtu.be/a7MWjOXk84Y
Correct behavior: https://youtu.be/WFdPb2vixQg