The RectangleSelector examples in the documentation ([here](https://matplotlib.org/gallery/widgets/rectangle_selector.html) and [here](https://matplotlib.org/api/widgets_api.html#matplotlib.widgets.RectangleSelector)) don't work properly in Jupyter notebooks. To fix, change the last line from: `show()` or `plt.show()` to `show(block=True)` or `plt.show(block=True)` Thanks!
