print(args.task[0]) TypeError: 'NoneType' object is not subscriptable

Question

def get_opts():
    model_names = sorted(
        name
        for name in models.__dict__
        if name.islower()
        and not name.startswith("__")
        and callable(models.__dict__[name])
    )

    # general setting
    parser = argparse.ArgumentParser(description="ACPL")
    parser.add_argument("--task", choices=["cx14", "cxp", "isic"], nargs="*", type=str)
    args = parser.parse_args(args=[])
    return args

args = get_opts()
print(args.task[0])

The following is the error message displayed:

TypeError                                 Traceback (most recent call last)
<ipython-input-33-5fd1fb76e64f> in <module>()
      1 args = get_opts()
----> 2 print(args.task[0])

TypeError: 'NoneType' object is not subscriptable

What did I do wrong? Why the type of "args.task" is "None"? Why not a "list"？