How to use the openpyn.credentials.check_credentials function in openpyn

# only clear/touch FW Rules if "-f" used
    elif force_fw_rules:
        firewall.clear_fw_rules()

    # check if OpenVPN config files exist if not download them.
    check_config_files()

    # if only positional argument used
    if country_code is None and server is None:
        country_code = country      # consider the positional arg e.g "us" same as "-c us"
    # if either "-c" or positional arg f.e "au" is present
    if country_code:
        # ask for and store credentials if not present, skip if "--test"
        if not test:
            if credentials.check_credentials() is False:
                credentials.save_credentials()

        if len(country_code) > 2:   # full country name
            # get the country_code from the full name
            country_code = api.get_country_code(full_name=country_code)
        country_code = country_code.lower()

        # keep trying to connect to new servers
        for tries in range(3):  # pylint: disable=W0612
            better_servers_list = find_better_servers(
                country_code, area, max_load, top_servers, tcp, p2p,
                dedicated, double_vpn, tor_over_vpn, anti_ddos, netflix, location, stats)
            pinged_servers_list = ping_servers(better_servers_list, pings, stats)
            chosen_servers = choose_best_servers(pinged_servers_list, stats)

            # connect to chosen_servers, if one fails go to next

# if "-f" used apply firewall rules
                if force_fw_rules:
                    network_interfaces = get_network_interfaces()
                    vpn_server_ip = get_vpn_server_ip(aserver, port)
                    firewall.apply_fw_rules(network_interfaces, vpn_server_ip, skip_dns_patch)
                    if internally_allowed:
                        firewall.internally_allow_ports(network_interfaces, internally_allowed)
                if nvram:
                    # TODO return 0 on success else 1 in asus.run()
                    asus.run(aserver, country_code, nvram, "All", "adaptive", "Strict", tcp, test)
                    logger.success("SAVED SERVER " + aserver + " ON PORT " + port + " TO NVRAM")
                return(connect(aserver, port, silent, test, skip_dns_patch, openvpn_options))
    elif server:
        # ask for and store credentials if not present, skip if "--test"
        if not test:
            if credentials.check_credentials() is False:
                credentials.save_credentials()

        server = server.lower()
        # if "-f" used apply firewall rules
        if force_fw_rules:
            network_interfaces = get_network_interfaces()
            vpn_server_ip = get_vpn_server_ip(server, port)
            firewall.apply_fw_rules(network_interfaces, vpn_server_ip, skip_dns_patch)
            if internally_allowed:
                firewall.internally_allow_ports(network_interfaces, internally_allowed)
        if nvram:
            asus.run(server, country_code, nvram, "All", "adaptive", "Strict", tcp, test)
            logger.success("SAVED SERVER " + server + " ON PORT " + port + " TO NVRAM")
            return 0
        for i in range(20):  # pylint: disable=W0612
            return(connect(server, port, silent, test, skip_dns_patch, openvpn_options))