docs: def get_assignable_gradebook_ids(self, gradebook_id):
          """Gets a list of gradebooks including and under the given gradebook node in which any grade system can be assigned.
  
          arg:    gradebook_id (osid.id.Id): the ``Id`` of the
                  ``Gradebook``
          return: (osid.id.IdList) - list of assignable gradebook ``Ids``
          raise:  NullArgument - ``gradebook_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          *compliance: mandatory -- This method must be implemented.*
  
          """
          # Implemented from template for
          # osid.resource.ResourceBinAssignmentSession.get_assignable_bin_ids
          # This will likely be overridden by an authorization adapter
          mgr = self._get_provider_manager('GRADING', local=True)
          lookup_session = mgr.get_gradebook_lookup_session(proxy=self._proxy)
          gradebooks = lookup_session.get_gradebooks()
          id_list = []
          for gradebook in gradebooks:
              id_list.append(gradebook.get_id())
          return IdList(id_list)