How to use the certbot.compat.os.path.join function in certbot

:param str cp_dir: checkpoint directory file path

        :raises errors.ReverterError: If unable to recover checkpoint

        """
        # Undo all commands
        if os.path.isfile(os.path.join(cp_dir, "COMMANDS")):
            self._run_undo_commands(os.path.join(cp_dir, "COMMANDS"))
        # Revert all changed files
        if os.path.isfile(os.path.join(cp_dir, "FILEPATHS")):
            try:
                with open(os.path.join(cp_dir, "FILEPATHS")) as paths_fd:
                    filepaths = paths_fd.read().splitlines()
                    for idx, path in enumerate(filepaths):
                        shutil.copy2(os.path.join(
                            cp_dir,
                            os.path.basename(path) + "_" + str(idx)), path)
            except (IOError, OSError):
                # This file is required in all checkpoints.
                logger.error("Unable to recover files from %s", cp_dir)
                raise errors.ReverterError(
                    "Unable to recover files from %s" % cp_dir)

        # Remove any newly added files if they exist
        self._remove_contained_files(os.path.join(cp_dir, "NEW_FILES"))

        try:
            shutil.rmtree(cp_dir)
        except OSError:
            logger.error("Unable to remove directory: %s", cp_dir)
            raise errors.ReverterError(

def _metadata_path(cls, account_dir_path):
        return os.path.join(account_dir_path, "meta.json")

:rtype: :class:`certbot.util.Key`

    :raises ValueError: If unable to generate the key given key_size.

    """
    try:
        key_pem = make_key(key_size)
    except ValueError as err:
        logger.error("", exc_info=True)
        raise err

    config = zope.component.getUtility(interfaces.IConfig)
    # Save file
    util.make_or_verify_dir(key_dir, 0o700, config.strict_permissions)
    key_f, key_path = util.unique_file(
        os.path.join(key_dir, keyname), 0o600, "wb")
    with key_f:
        key_f.write(key_pem)
    logger.debug("Generating key (%d bits): %s", key_size, key_path)

    return util.Key(key_path, key_pem)

def __init__(self, configurator):
        super(TLSSNI01, self).__init__(configurator)
        self.challenge_conf = os.path.join(
            configurator.config.config_dir, "le_tls_sni_01_cert_challenge.conf")
        # self.completed = 0

:param str link: Path to a symbolic link

    :returns: Absolute path to the target of link
    :rtype: str

    :raises .CertStorageError: If link does not exists.

    """
    try:
        target = os.readlink(link)
    except OSError:
        raise errors.CertStorageError(
            "Expected {0} to be a symlink".format(link))

    if not os.path.isabs(target):
        target = os.path.join(os.path.dirname(link), target)
    return os.path.abspath(target)

def _regr_path(cls, account_dir_path):
        return os.path.join(account_dir_path, "regr.json")

"""Finalize the checkpoint.

        Timestamps and permanently saves all changes made through the use
        of :func:`~add_to_checkpoint` and :func:`~register_file_creation`

        :param str title: Title describing checkpoint

        :raises certbot.errors.ReverterError: when the
            checkpoint is not able to be finalized.

        """
        # Check to make sure an "in progress" directory exists
        if not os.path.isdir(self.config.in_progress_dir):
            return

        changes_since_path = os.path.join(self.config.in_progress_dir, "CHANGES_SINCE")
        changes_since_tmp_path = os.path.join(self.config.in_progress_dir, "CHANGES_SINCE.tmp")

        if not os.path.exists(changes_since_path):
            logger.info("Rollback checkpoint is empty (no changes made?)")
            with open(changes_since_path, 'w') as f:
                f.write("No changes\n")

        # Add title to self.config.in_progress_dir CHANGES_SINCE
        try:
            with open(changes_since_tmp_path, "w") as changes_tmp:
                changes_tmp.write("-- %s --\n" % title)
                with open(changes_since_path, "r") as changes_orig:
                    changes_tmp.write(changes_orig.read())

        # Move self.config.in_progress_dir to Backups directory
            shutil.move(changes_since_tmp_path, changes_since_path)

def _key_path(cls, account_dir_path):
        return os.path.join(account_dir_path, "private_key.json")

def _metadata_path(cls, account_dir_path):
        return os.path.join(account_dir_path, "meta.json")