How to use the letsencrypt.configuration.RenewerConfiguration function in letsencrypt

def _find_duplicative_certs(domains, config, renew_config):
    """Find existing certs that duplicate the request."""

    identical_names_cert, subset_names_cert = None, None

    configs_dir = renew_config.renewal_configs_dir
    # Verify the directory is there
    le_util.make_or_verify_dir(configs_dir, mode=0o755, uid=os.geteuid())

    cli_config = configuration.RenewerConfiguration(config)
    for renewal_file in os.listdir(configs_dir):
        try:
            full_path = os.path.join(configs_dir, renewal_file)
            rc_config = configobj.ConfigObj(renew_config.renewer_config_file)
            rc_config.merge(configobj.ConfigObj(full_path))
            rc_config.filename = full_path
            candidate_lineage = storage.RenewableCert(
                rc_config, config_opts=None, cli_config=cli_config)
        except (configobj.ConfigObjError, errors.CertStorageError, IOError):
            logger.warning("Renewal configuration file %s is broken. "
                           "Skipping.", full_path)
            continue
        # TODO: Handle these differently depending on whether they are
        #       expired or still valid?
        candidate_names = set(candidate_lineage.names())
        if candidate_names == set(domains):

#       called renewer_enabled.)

    # TODO: When we have a more elaborate renewer command line, we will
    #       presumably also be able to specify a config file on the
    #       command line, which, if provided, should take precedence over
    #       te default config files

    zope.component.provideUtility(display_util.FileDisplay(sys.stdout))

    args = _create_parser().parse_args(cli_args)

    uid = os.geteuid()
    le_util.make_or_verify_dir(args.logs_dir, 0o700, uid)
    cli.setup_logging(args, _cli_log_handler, logfile='renewer.log')

    cli_config = configuration.RenewerConfiguration(args)

    # Ensure that all of the needed folders have been created before continuing
    le_util.make_or_verify_dir(cli_config.work_dir,
                               constants.CONFIG_DIRS_MODE, uid)

    for renewal_file in os.listdir(cli_config.renewal_configs_dir):
        print "Processing", renewal_file
        try:
            # TODO: Before trying to initialize the RenewableCert object,
            #       we could check here whether the combination of the config
            #       and the rc_config together disables all autorenewal and
            #       autodeployment applicable to this cert.  In that case, we
            #       can simply continue and don't need to instantiate a
            #       RenewableCert object for this cert at all, which could
            #       dramatically improve performance for large deployments
            #       where autorenewal is widely turned off.

if (self.config.config_dir != constants.CLI_DEFAULTS["config_dir"] or
                self.config.work_dir != constants.CLI_DEFAULTS["work_dir"]):
            logger.warning(
                "Non-standard path(s), might not work with crontab installed "
                "by your operating system package manager")

        if self.config.dry_run:
            logger.info("Dry run: Skipping creating new lineage for %s",
                        domains[0])
            return None
        else:
            return storage.RenewableCert.new_lineage(
                domains[0], OpenSSL.crypto.dump_certificate(
                    OpenSSL.crypto.FILETYPE_PEM, certr.body.wrapped),
                key.pem, crypto_util.dump_pyopenssl_chain(chain),
                configuration.RenewerConfiguration(self.config.namespace))

def __init__(self, plugins, config):
        self.installers = _extract_avail_installers(plugins, config)
        self.config = configuration.RenewerConfiguration(config)

        self.csha1_vhost = self._get_installed_locations()

        self.certs = self._get_renewable_certs()

        # Path was chosen instead of sha1 because, we are only checking certs
        # in our immediate database.  There is no fear, as in installed case,
        # where we may not recognize the path, but it is the same cert.
        self.cpath_validity = _get_validity_info(self.certs)

:returns: RenewableCert or None if renewal shouldn't occur.
    :rtype: :class:`.storage.RenewableCert`

    :raises .Error: If the user would like to rerun the client again.

    """
    renewal = False

    # Considering the possibility that the requested certificate is
    # related to an existing certificate.  (config.duplicate, which
    # is set with --duplicate, skips all of this logic and forces any
    # kind of certificate to be obtained with renewal = False.)
    if not config.duplicate:
        ident_names_cert, subset_names_cert = _find_duplicative_certs(
            domains, config, configuration.RenewerConfiguration(config))
        # I am not sure whether that correctly reads the systemwide
        # configuration file.
        question = None
        if ident_names_cert is not None:
            question = (
                "You have an existing certificate that contains exactly the "
                "same domains you requested (ref: {0}){br}{br}Do you want to "
                "renew and replace this certificate with a newly-issued one?"
            ).format(ident_names_cert.configfile.filename, br=os.linesep)
        elif subset_names_cert is not None:
            question = (
                "You have an existing certificate that contains a portion of "
                "the domains you requested (ref: {0}){br}{br}It contains these "
                "names: {1}{br}{br}You requested these names for the new "
                "certificate: {2}.{br}{br}Do you want to replace this existing "
                "certificate with the new certificate?"