docs: def get_gradebook_nodes(self, gradebook_id, ancestor_levels, descendant_levels, include_siblings):
          """Gets a portion of the hierarchy for the given gradebook.
  
          arg:    gradebook_id (osid.id.Id): the ``Id`` to query
          arg:    ancestor_levels (cardinal): the maximum number of
                  ancestor levels to include. A value of 0 returns no
                  parents in the node.
          arg:    descendant_levels (cardinal): the maximum number of
                  descendant levels to include. A value of 0 returns no
                  children in the node.
          arg:    include_siblings (boolean): ``true`` to include the
                  siblings of the given node, ``false`` to omit the
                  siblings
          return: (osid.grading.GradebookNode) - a gradebook node
          raise:  NotFound - ``gradebook_id`` is not found
          raise:  NullArgument - ``gradebook_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*
  
          """
          # Implemented from template for
          # osid.resource.BinHierarchySession.get_bin_nodes
          return objects.GradebookNode(self.get_gradebook_node_ids(
              gradebook_id=gradebook_id,
              ancestor_levels=ancestor_levels,
              descendant_levels=descendant_levels,
              include_siblings=include_siblings)._my_map, runtime=self._runtime, proxy=self._proxy)