def get_root_gradebooks(self):
<EOL>if self._catalog_session is not None:<EOL><INDENT>return self._catalog_session.get_root_catalogs()<EOL><DEDENT>return GradebookLookupSession(<EOL>self._proxy,<EOL>self._runtime).get_gradebooks_by_ids(list(self.get_root_gradebook_ids()))<EOL>
Gets the root gradebooks in this gradebook hierarchy.

        return: (osid.grading.GradebookList) - the root gradebooks
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        *compliance: mandatory -- This method is must be implemented.*