def __missing__(self, key):
        if self.default_factory is None:
            raise KeyError(key)
        else:
            ret = self[key] = self.default_factory(name=key)
            return ret
def __getitem__(self, key):
        logger.debug("Get /%s config key", "/".join(self._path + (key,)))
        value = self._collection[key]
        return self._to_python(value)