cmd.py

def providesSubscriptionAdapter(cls):
    provideSubscriptionAdapter(cls, adapts=[cls])
    return cls


@providesSubscriptionAdapter
class cmd_ls(Cmd):

    implements(ICmdArgumentsSyntax)

    def arguments(self):
        parser = VirtualConsoleArgumentParser()
        parser.add_argument("-l")
        parser.add_argument("paths", nargs="*")
        return parser

user.py

arg_parsers = querySubscriptions(self.cmd, ICmdArgumentsSyntax)