How to use the briefcase.__version__ function in briefcase

def test_bare_command_version(capsys):
    "``briefcase create -V`` returns the version"
    with pytest.raises(SystemExit) as excinfo:
        parse_cmdline('create -V'.split())

    # Normal exit due to displaying help
    assert excinfo.value.code == 0
    # Version is displayed.
    output = capsys.readouterr().out
    assert output == '{__version__}\n'.format(__version__=__version__)

def test_version_only(capsys):
    "``briefcase -V`` returns current version"
    with pytest.raises(SystemExit) as excinfo:
        parse_cmdline('-V'.split())

    # Normal exit due to displaying help
    assert excinfo.value.code == 0
    # Version is displayed.
    output = capsys.readouterr().out
    assert output == '{__version__}\n'.format(__version__=__version__)

description="Package Python code for distribution.",
        usage="briefcase [-h]  [] [] ...",
        epilog="Each command, platform and format has additional options. "
               "Use the -h option on a specific command for more details.",
        add_help=False
    )
    parser.add_argument(
        '-f', '--formats',
        action='store_true',
        dest='show_output_formats',
        help="show the available output formats and exit (specify a platform for more details)."
    )
    parser.add_argument(
        '-V', '--version',
        action='version',
        version=__version__
    )

    #  isn't actually optional; but if it's marked as required,
    # there's no way to get help for subcommands. So; treat 
    # as optional, handle the case where  isn't provided
    # as the case where top-level help is displayed, and provide an explicit
    # usage string so that the instructions displayed are correct
    parser.add_argument(
        'command',
        choices=[
            'new', 'dev', 'create', 'update', 'build', 'run', 'package', 'publish'
        ],
        metavar='command',
        nargs='?',
        help='the command to execute (one of: %(choices)s)',
    )

def add_default_options(self, parser):
        """
        Add the default options that exist on *all* commands

        :param parser: a stub argparse parser for the command.
        """
        parser.add_argument(
            '-v', '--verbosity',
            action='count',
            default=1,
            help="set the verbosity of output"
        )
        parser.add_argument(
            '-V', '--version',
            action='version',
            version=__version__
        )