code: def nodes(self):
          
          if not hasattr(self, '_nodes'):
              base_url = "{}/{}".format(NodeBalancerConfig.api_endpoint, NodeBalancerNode.derived_url_path)
              result = self._client._get_objects(base_url, NodeBalancerNode, model=self, parent_id=(self.id, self.nodebalancer_id))
  
              self._set('_nodes', result)
  
          return self._nodes
docs: This is a special derived_class relationship because NodeBalancerNode is the
          only api object that requires two parent_ids