code: def num_classes(self):
      segments = self.class_to_segments.values()
      num = 0
      for seg in segments:
          num = max(num, max(seg))
      return num + 1
  
imports: import torch
  import glob
  import os
  from torch_geometric.io import read_txt_array
  from torch_geometric.data.data import Data
  import torch_geometric.transforms
  from torch_geometric.nn import knn_interpolate
  import numpy
  import logging
  from torch_points3d.core.data_transform import SaveOriginalPosId
  from torch_points3d.utils import is_list
  from torch_points3d.datasets.base_dataset import BaseDataset
  from torch_points3d.metrics.shapenet_part_tracker import ShapenetPartTracker
  from torch_points3d.datasets.segmentation.shapenet import ShapeNet
label_desc: Use image node_id 5 for calling the ForwardShapenetDataset obj's underlying member method code with example usage: obj.num_classes() and returns: unknown