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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _parse_directory(self):
 """ Parse the storage directory in the config. Returns: str """

        if self._parser.has_option('storage', 'directory'):
            directory = self._parser.get('storage', 'directory')
            # Don't allow CUSTOM_APPS_DIR as a storage directory
            if directory == CUSTOM_APPS_DIR:
                raise ConfigError("{} cannot be used as a storage directory."
                                  .format(CUSTOM_APPS_DIR))
        else:
            directory = MACKUP_BACKUP_PATH

        return str(directory)