How to use the manubot.manuscript.datetime_now function in manubot

"""
    # Generated manuscript variables
    variables = collections.OrderedDict()

    # Read metadata which contains pandoc_yaml_metadata
    # as well as author_info.
    if args.meta_yaml_path.is_file():
        with args.meta_yaml_path.open() as read_file:
            metadata = yaml.load(read_file)
            assert isinstance(metadata, dict)
    else:
        metadata = {}
        logging.warning(f'missing {args.meta_yaml_path} file with yaml_metadata_block for pandoc')

    # Add date to metadata
    now = datetime_now()
    logging.info(
        f'Using {now:%Z} timezone.\n'
        f'Dating manuscript with the current datetime: {now.isoformat()}')
    metadata['date-meta'] = now.date().isoformat()
    variables['date'] = f'{now:%B} {now.day}, {now.year}'

    # Process authors metadata
    authors = metadata.pop('author_info', [])
    metadata['author-meta'] = [author['name'] for author in authors]
    variables['authors'] = authors
    variables = add_author_affiliations(variables)

    # Set repository version metadata for Travis CI builds only
    # https://docs.travis-ci.com/user/environment-variables/
    if os.getenv('TRAVIS', 'false') == 'true':
        repo_slug = os.environ['TRAVIS_REPO_SLUG']