def get_catalog_hierarchy_design_session(self):
raise Unimplemented()<EOL>
Gets the catalog hierarchy design session.

        return: (osid.cataloging.CatalogHierarchyDesignSession) - a
                ``CatalogHierarchyDesignSession``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_catalog_hierarchy_design()``
                is ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_catalog_hierarchy_design()`` is ``true``.*