actual.py

parser = argparse.ArgumentParser()

parser.addArgument('--print-metadata')
subparsers = parser.add_subparsers(dest='command')
subparsers.add_parser(name='build')
subparsers.add_parser(name='predict')

parsed_args = parser.parse_args()

match vars(parsed_args):
    case { "command": "build" }:
        raise 'implement build!'
    case { "command": "predict" }:
        raise 'implement predict!'
    case { "print_metadata": blob_path }:
        raise 'implement --print-metadata for path '+blob_path

desired.py

parsed_args = above() # argparse config as above...

match parsed_args: 
    case { .command == "build" }:
        raise 'implement build!'
    case { .command == "predict" }:
        raise 'implement predict!'
    case { blob_path = .print_metadata }:
        raise 'implement --print-metadata for path '+blob_path