docs: def get_root_gradebooks(self):
          """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.*
  
          """
          # Implemented from template for
          # osid.resource.BinHierarchySession.get_root_bins
          if self._catalog_session is not None:
              return self._catalog_session.get_root_catalogs()
          return GradebookLookupSession(
              self._proxy,
              self._runtime).get_gradebooks_by_ids(list(self.get_root_gradebook_ids()))