Dockerfile for image built off Ubuntu 20.04 containing Python 3.10 (3.6, 3.7, 3.8, 3.9) built from source ...
These classes weren't introduced with the first release of Python 3.9.0 but with Python 3.9.1. See comparison between Python 3.9.0 and 3.9.1: python/cpython@v3.9.0...v3.9.1 The conditional import in ...