load configuration from config/

def _load_config(self):
        """load configuration from config/"""
        logger.debug(
            'Listing per-account config subdirectories in %s', self._conf_dir
        )
        for acct_id in os.listdir(self._conf_dir):
            path = os.path.join(self._conf_dir, acct_id)
            # skip if not a directory
            if not os.path.isdir(path):
                continue
            # skip if doesn't match ^[0-9]+$
            if not self.acct_id_re.match(acct_id):
                continue
            # call _load_account specifying the directory name (acct ID) & path
            self._load_account(acct_id, path)
        # Once all configuration is loaded, build a dict of Account Name to
        # Account ID (``self._acct_name_to_id``) for faster access to configs
        # by name.
        for acct_id, data in self._config.items():
            if data['name'] is None:
                continue
            self._acct_name_to_id[data['name']] = acct_id