code: def __init__(self):
      self.num_classes = 2
  
imports: import unittest
  import torch
  import numpy
  import os
  import random
  import sys
  from torch_geometric.data import Data
  from torch_points3d.utils.geometry import rodrigues
  from torch_points3d.metrics.registration_tracker import FragmentRegistrationTracker
label_desc: Use image node_id 1 to create a new MockDataset object  with example: obj = MockDataset()