Sometimes I need to use argparse like this:


>>> parser = argparse.ArgumentParser(prog='PROG')
>>> group = parser.add_mutually_dependence_group()
>>> group.add_argument('--foo')
>>> group.add_argument('--bar')
>>> parser.parse_args(['--foo', 'f', '--bar', 'b'])
Namespace(bar='b', foo='f')
>>> parser.parse_args(['--foo', 'f'])
PROG: error: --foo dependence on --bar
>>> parser.parse_args(['--bar', 'b'])
PROG: error: --bar dependence on --foo

I have some optional argument. but if any argument in a group was present on the command line. i need the others must also was present on. so i think ``add_mutually_dependence_group`` does make sense.