[docs] [issue14149] argparse: Document how to use argument names that are not Python identifiers

Change by Fred L. Drake, Jr. <fdrake@gmail.com>: ---------- versions: +Python 3.7, Python 3.8, Python 3.9 -Python 3.2, Python 3.3 _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue14149> _______________________________________