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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def toxcmd_main(args=None):
 """Command util with subcommands for tox environments."""

    usage = "USAGE: %(prog)s [OPTIONS] COMMAND args..."
    if args is None:
        args = sys.argv[1:]

    # -- STEP: Build command-line parser.
    parser = argparse.ArgumentParser(description=inspect.getdoc(toxcmd_main),
                                     formatter_class=FORMATTER_CLASS)
    common_parser = parser.add_argument_group("Common options")
    common_parser.add_argument("--version", action="version", version=VERSION)
    subparsers = parser.add_subparsers(help="commands")
    for command in discover_commands():
        command_parser = subparsers.add_parser(command.name,
                                               usage=command.usage,
                                               description=command.description,
                                               help=command.short_description,
                                               formatter_class=FORMATTER_CLASS)
        command_parser.set_defaults(func=command)
        command.setup_parser(command_parser)
        command.parser = command_parser

    # -- STEP: Process command-line and run command.
    options = parser.parse_args(args)
    command_function = options.func
    return command_function(options)