def get_root_catalogs(self):
<EOL>if self._catalog_session is not None:<EOL><INDENT>return self._catalog_session.get_root_catalogs()<EOL><DEDENT>return CatalogLookupSession(<EOL>self._proxy,<EOL>self._runtime).get_catalogs_by_ids(list(self.get_root_catalog_ids()))<EOL>
Gets the root catalogs in the catalog hierarchy.

        A node with no parents is an orphan. While all catalog ``Ids``
        are known to the hierarchy, an orphan does not appear in the
        hierarchy unless explicitly added as a root node or child of
        another node.

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