docstr: Returns a list of classes that are not instances
          
docstr_tok: ["Returns","a","list","of","classes","that","are","not","instances"]
code: def stuff_classes(self):
      """Returns a list of classes that are not instances"""
      return self.train_dataset.stuff_classes
  
imports: import os
  import numpy
  import torch
  import logging
  from torch_geometric.data import InMemoryDataset
  from torch_points3d.datasets.segmentation.scannet import Scannet
  from torch_points3d.metrics.panoptic_tracker import PanopticTracker
  from torch_points3d.datasets.base_dataset import BaseDataset, save_used_properties
  from torch_points3d.datasets.panoptic.utils import set_extra_labels
label_desc: Use image node_id 2 for calling the ScannetDataset obj's underlying member method code with example usage: obj.stuff_classes() and returns: self