Create a generator.

    Parameters
    ----------
    args : `argparse.Namespace`
        Command arguments.

def cmd_create(args):
    """Create a generator.

    Parameters
    ----------
    args : `argparse.Namespace`
        Command arguments.
    """
    if args.type == SQLITE:
        if args.output is not None and path.exists(args.output):
            remove(args.output)
        storage = SqliteStorage(db=args.output, settings=args.settings)
    else:
        storage = JsonStorage(settings=args.settings)
    markov = MarkovText.from_storage(storage)
    read(args.input, markov, args.progress)
    save(markov, args.output, args)