def get_metadata(self, refresh=True):
        """
        return cached metadata by default

        :param refresh: bool, update the metadata with up to date content
        :return: dict
        """
        if refresh or not self._metadata:
            ident = self._id or self.get_full_name()
            if not ident:
                raise ConuException(
                    "This image does not have a valid identifier.")
            self._metadata = dict()
        return self._metadata
return cached metadata by default

        :param refresh: bool, update the metadata with up to date content
        :return: dict