When I use this example:https://matplotlib.org/3.1.3/gallery/widgets/polygon_selector_demo.html
and want to use blitting (see line below), the selection polygon dissapears when polygon is finalized.

self.poly=PolygonSelector(ax,self.onselect,useblit=True)

**Matplotlib version: 3.1.2 **

• Operating system: Ubuntu 16.04
• Matplotlib version: 3.1.2 (from pipy.org)
• Matplotlib backend (`Qt5Agg'):
• Python version: 3.7.6
• Other libraries: PySide2 - 5.14.2