How to use the nhentai.logger.logger.warning function in nhentai

def _download_callback(self, request, result):
        result, data = result
        if result == 0:
            logger.warning('fatal errors occurred, ignored')
            # exit(1)
        elif result == -1:
            logger.warning('url {} return status code 404'.format(data))
        else:
            logger.log(15, '{0} downloaded successfully'.format(data))

if proxy_url.scheme not in ('http', 'https'):
                logger.error('Invalid protocol \'{0}\' of proxy, ignored'.format(proxy_url.scheme))
            else:
                with open(constant.NHENTAI_PROXY, 'w') as f:
                    f.write(args.proxy)

        except Exception as e:
            logger.error('Cannot create NHENTAI_HOME: {}'.format(str(e)))
            exit(1)

        logger.info('Proxy \'{0}\' saved.'.format(args.proxy))
        exit(0)

    if args.favorites:
        if not constant.COOKIE:
            logger.warning('Cookie has not been set, please use `nhentai --cookie \'COOKIE\'` to set it.')
            exit(1)

    if args.id:
        _ = [i.strip() for i in args.id.split(',')]
        args.id = set(int(i) for i in _ if i.isdigit())

    if args.file:
        with open(args.file, 'r') as f:
            _ = [i.strip() for i in f.readlines()]
            args.id = set(int(i) for i in _ if i.isdigit())

    if (args.is_download or args.is_show) and not args.id and not args.keyword and not args.favorites:
        logger.critical('Doujinshi id(s) are required for downloading')
        parser.print_help()
        exit(1)

name = doujinshi_obj.name.encode('utf-8')
    else:
        name = {'title': 'nHentai HTML Viewer'}

    data = html.format(TITLE=name, IMAGES=image_html, SCRIPTS=js, STYLES=css)
    try:
        if sys.version_info < (3, 0):
            with open(os.path.join(doujinshi_dir, 'index.html'), 'w') as f:
                f.write(data)
        else:
            with open(os.path.join(doujinshi_dir, 'index.html'), 'wb') as f:
                f.write(data.encode('utf-8'))

        logger.log(15, 'HTML Viewer has been written to \'{0}\''.format(os.path.join(doujinshi_dir, 'index.html')))
    except Exception as e:
        logger.warning('Writing HTML Viewer failed ({})'.format(str(e)))

def login(username, password):
    logger.warning('This feature is deprecated, please use --cookie to set your cookie.')
    csrf_token = _get_csrf_token(request('get', url=constant.LOGIN_URL).text)
    if os.getenv('DEBUG'):
        logger.info('Getting CSRF token ...')

    if os.getenv('DEBUG'):
        logger.info('CSRF token is {}'.format(csrf_token))

    login_dict = {
        'csrfmiddlewaretoken': csrf_token,
        'username_or_email': username,
        'password': password,
    }
    resp = request('post', url=constant.LOGIN_URL, data=login_dict)

    if 'You\'re loading pages way too quickly.' in resp.text or 'Really, slow down' in resp.text:
        csrf_token = _get_csrf_token(resp.text)

logger.critical(str(e))
                            return 0, None
                        continue

                    break

                length = response.headers.get('content-length')
                if length is None:
                    f.write(response.content)
                else:
                    for chunk in response.iter_content(2048):
                        f.write(chunk)

        except (requests.HTTPError, requests.Timeout) as e:
            if retried < 3:
                logger.warning('Warning: {0}, retrying({1}) ...'.format(str(e), retried))
                return 0, self._download(url=url, folder=folder, filename=filename, retried=retried+1)
            else:
                return 0, None

        except NhentaiImageNotExistException as e:
            os.remove(os.path.join(folder, base_filename.zfill(3) + extension))
            return -1, url

        except Exception as e:
            logger.critical(str(e))
            return 0, None

        return 1, url

from nhentai.constant import PROXY
    # constant.PROXY will be changed after cmd_parser()
    if PROXY != {}:
        logger.info('Using proxy: {0}'.format(PROXY))

    # check your cookie
    check_cookie()

    index = 0
    doujinshis = []
    doujinshi_ids = []
    doujinshi_list = []

    if options.favorites:
        if not options.is_download:
            logger.warning('You do not specify --download option')

        doujinshis = favorites_parser(options.page_range)

    elif options.tag:
        doujinshis = tag_parser(options.tag, sorting=options.sorting, max_page=options.max_page)

    elif options.artist:
        index = 1

    elif options.character:
        index = 2

    elif options.parody:
        index = 3

    elif options.group:

files.sort()

        if 'index.html' in files:
            logger.info('Add doujinshi \'{}\''.format(folder))
        else:
            continue

        image = files[0]  # 001.jpg or 001.png
        if folder is not None:
            title = folder.replace('_', ' ')
        else:
            title = 'nHentai HTML Viewer'

        image_html += element.format(FOLDER=folder, IMAGE=image, TITLE=title)
    if image_html == '':
        logger.warning('No index.html found, --gen-main paused.')
        return
    try:
        data = main.format(STYLES=css, SCRIPTS=js, PICTURE=image_html)
        if sys.version_info < (3, 0):
            with open('./main.html', 'w') as f:
                f.write(data)
        else:
            with open('./main.html', 'wb') as f:
                f.write(data.encode('utf-8'))
        shutil.copy(os.path.dirname(__file__)+'/viewer/logo.png', './')
        set_js_database()
        logger.log(
            15, 'Main Viewer has been written to \'{0}main.html\''.format(output_dir))
    except Exception as e:
        logger.warning('Writing Main Viewer failed ({})'.format(str(e)))

logger.warning('No index.html found, --gen-main paused.')
        return
    try:
        data = main.format(STYLES=css, SCRIPTS=js, PICTURE=image_html)
        if sys.version_info < (3, 0):
            with open('./main.html', 'w') as f:
                f.write(data)
        else:
            with open('./main.html', 'wb') as f:
                f.write(data.encode('utf-8'))
        shutil.copy(os.path.dirname(__file__)+'/viewer/logo.png', './')
        set_js_database()
        logger.log(
            15, 'Main Viewer has been written to \'{0}main.html\''.format(output_dir))
    except Exception as e:
        logger.warning('Writing Main Viewer failed ({})'.format(str(e)))