How to use the nhentai.constant function in nhentai

if args.html_viewer:
        generate_html()
        exit(0)

    if args.main_viewer and not args.id and not args.keyword and not args.favorites:
        generate_main_html()
        exit(0)

    if args.clean_download_history:
        with DB() as db:
            db.clean_all()

        logger.info('Download history cleaned.')
        exit(0)

    if os.path.exists(constant.NHENTAI_COOKIE):
        with open(constant.NHENTAI_COOKIE, 'r') as f:
            constant.COOKIE = f.read()

    if args.cookie:
        try:
            if not os.path.exists(constant.NHENTAI_HOME):
                os.mkdir(constant.NHENTAI_HOME)

            with open(constant.NHENTAI_COOKIE, 'w') as f:
                f.write(args.cookie)
        except Exception as e:
            logger.error('Cannot create NHENTAI_HOME: {}'.format(str(e)))
            exit(1)

        logger.info('Cookie saved.')
        exit(0)

if args.cookie:
        try:
            if not os.path.exists(constant.NHENTAI_HOME):
                os.mkdir(constant.NHENTAI_HOME)

            with open(os.path.join(constant.NHENTAI_HOME, 'cookie'), 'w') as f:
                f.write(args.cookie)
        except Exception as e:
            logger.error('Cannot create NHENTAI_HOME: {}'.format(str(e)))
            exit(1)

        logger.info('Cookie saved.')
        exit(0)

    if os.path.exists(os.path.join(constant.NHENTAI_HOME, 'proxy')):
        with open(os.path.join(constant.NHENTAI_HOME, 'proxy'), 'r') as f:
            link = f.read()
            constant.PROXY = {'http': link, 'https': link}

    if args.proxy:
        try:
            if not os.path.exists(constant.NHENTAI_HOME):
                os.mkdir(constant.NHENTAI_HOME)

            proxy_url = urlparse(args.proxy)
            if proxy_url.scheme not in ('http', 'https'):
                logger.error('Invalid protocol \'{0}\' of proxy, ignored'.format(proxy_url.scheme))
            else:
                with open(os.path.join(constant.NHENTAI_HOME, 'proxy'), 'w') as f:
                    f.write(args.proxy)
        except Exception as e:
            logger.error('Cannot create NHENTAI_HOME: {}'.format(str(e)))

def doujinshi_parser(id_):
    if not isinstance(id_, (int,)) and (isinstance(id_, (str,)) and not id_.isdigit()):
        raise Exception('Doujinshi id({0}) is not valid'.format(id_))

    id_ = int(id_)
    logger.log(15, 'Fetching doujinshi information of id {0}'.format(id_))
    doujinshi = dict()
    doujinshi['id'] = id_
    url = '{0}/{1}/'.format(constant.DETAIL_URL, id_)

    try:
        response = request('get', url)
        if response.status_code in (200, ):
            response = response.content
        else:
            logger.debug('Slow down and retry ({}) ...'.format(id_))
            time.sleep(1)
            return doujinshi_parser(str(id_))

    except Exception as e:
        logger.warn('Error: {}, ignored'.format(str(e)))
        return None

    html = BeautifulSoup(response, 'html.parser')
    doujinshi_info = html.find('div', attrs={'id': 'info'})

if args.cookie:
        try:
            if not os.path.exists(constant.NHENTAI_HOME):
                os.mkdir(constant.NHENTAI_HOME)

            with open(constant.NHENTAI_COOKIE, 'w') as f:
                f.write(args.cookie)
        except Exception as e:
            logger.error('Cannot create NHENTAI_HOME: {}'.format(str(e)))
            exit(1)

        logger.info('Cookie saved.')
        exit(0)

    if os.path.exists(constant.NHENTAI_LANGUAGE) and not args.language:
        with open(constant.NHENTAI_LANGUAGE, 'r') as f:
            constant.LANGUAGE = f.read()
            args.language = f.read()

    if args.language:
        try:
            if not os.path.exists(constant.NHENTAI_HOME):
                os.mkdir(constant.NHENTAI_HOME)

            with open(constant.NHENTAI_LANGUAGE, 'w') as f:
                f.write(args.language)
        except Exception as e:
            logger.error('Cannot create NHENTAI_HOME: {}'.format(str(e)))
            exit(1)

        logger.info('Default language now is {}.'.format(args.language))
        exit(0)

def __enter__(self):
        self.conn = sqlite3.connect(constant.NHENTAI_HISTORY)
        self.cur = self.conn.cursor()
        self.cur.execute('CREATE TABLE IF NOT EXISTS download_history (id text)')
        self.conn.commit()
        return self