How to use the xandikos.store.config.FILENAME function in xandikos

def __init__(self, path, check_for_duplicate_uids=True):
        super(VdirStore, self).__init__(MemoryIndex())
        self.path = path
        self._check_for_duplicate_uids = check_for_duplicate_uids
        # Set of blob ids that have already been scanned
        self._fname_to_uid = {}
        # Maps uids to (sha, fname)
        self._uid_to_fname = {}
        cp = configparser.ConfigParser()
        cp.read([os.path.join(self.path, CONFIG_FILENAME)])

        def save_config(cp, message):
            with open(os.path.join(self.path, CONFIG_FILENAME), 'w') as f:
                cp.write(f)
        self.config = FileBasedCollectionMetadata(cp, save=save_config)

def save_config(cp, message):
                f = StringIO()
                cp.write(f)
                self._import_one(
                    CONFIG_FILENAME, [f.getvalue().encode('utf-8')],
                    message)
            return FileBasedCollectionMetadata(cp, save=save_config)

def _iterblobs(self, ctag=None):
        if ctag is None:
            tree = self._get_current_tree()
        else:
            tree = self.repo.object_store[ctag.encode('ascii')]
        for (name, mode, sha) in tree.iteritems():
            name = name.decode(DEFAULT_ENCODING)
            if name == CONFIG_FILENAME:
                continue
            yield (name, mode, sha)

def config(self):
        if RepoCollectionMetadata.present(self.repo):
            return RepoCollectionMetadata(self.repo)
        else:
            cp = configparser.ConfigParser()
            try:
                cf = self._get_raw(CONFIG_FILENAME)
            except KeyError:
                pass
            else:
                if cf is not None:
                    cp.read_string(b''.join(cf).decode('utf-8'))

            def save_config(cp, message):
                f = StringIO()
                cp.write(f)
                self._import_one(
                    CONFIG_FILENAME, [f.getvalue().encode('utf-8')],
                    message)
            return FileBasedCollectionMetadata(cp, save=save_config)

def iter_with_etag(self, ctag=None):
        """Iterate over all items in the store with etag.

        :param ctag: Ctag to iterate for
        :yield: (name, content_type, etag) tuples
        """
        for name in os.listdir(self.path):
            if name.endswith('.tmp'):
                continue
            if name == CONFIG_FILENAME:
                continue
            if name.endswith('.ics'):
                content_type = 'text/calendar'
            elif name.endswith('.vcf'):
                content_type = 'text/vcard'
            else:
                continue
            yield (name, content_type, self._get_etag(name))