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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 parse():
 """Parse the command line inputs and execute the subcommand."""


    # Build the list of subcommand modules
    modnames = [mod for (_, mod, _)
                in pkgutil.iter_modules(payu.subcommands.__path__,
                                        prefix=payu.subcommands.__name__ + '.')
                if mod.endswith('_cmd')]

    subcmds = [importlib.import_module(mod) for mod in modnames]

    # Construct the subcommand parser
    parser = argparse.ArgumentParser()
    parser.add_argument('--version', action='version',
                        version='payu {0}'.format(payu.__version__))

    subparsers = parser.add_subparsers()

    for cmd in subcmds:
        cmd_parser = subparsers.add_parser(cmd.title, **cmd.parameters)
        cmd_parser.set_defaults(run_cmd=cmd.runcmd)

        for arg in cmd.arguments:
            cmd_parser.add_argument(*arg['flags'], **arg['parameters'])

    # Display help if no arguments are provided
    if len(sys.argv) == 1:
        parser.print_help()
    else:
        args = vars(parser.parse_args())
        run_cmd = args.pop('run_cmd')
        run_cmd(**args)