def get_root_vault_ids(self):
<EOL>if self._catalog_session is not None:<EOL><INDENT>return self._catalog_session.get_root_catalog_ids()<EOL><DEDENT>return self._hierarchy_session.get_roots()<EOL>
Gets the root vault ``Ids`` in this hierarchy.

        return: (osid.id.IdList) - the root vault ``Ids``
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        *compliance: mandatory -- This method must be implemented.*