code: def get_objective_bank_nodes(self, objective_bank_id, ancestor_levels, descendant_levels, include_siblings):
          
          # Implemented from template for
          # osid.resource.BinHierarchySession.get_bin_nodes
          return objects.ObjectiveBankNode(self.get_objective_bank_node_ids(
              objective_bank_id=objective_bank_id,
              ancestor_levels=ancestor_levels,
              descendant_levels=descendant_levels,
              include_siblings=include_siblings)._my_map, runtime=self._runtime, proxy=self._proxy)
docs: Gets a portion of the hierarchy for the given objective bank.
  
          arg:    objective_bank_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.learning.ObjectiveBankNode) - an objective bank
                  node
          raise:  NotFound - ``objective_bank_id`` not found
          raise:  NullArgument - ``objective_bank_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*