code: def __len__(self):
      size_dataset = len(os.listdir(self.path_data))
      if self.is_offline:
          size_dataset = size_dataset // 2
      return size_dataset
  
imports: import numpy
  import os
  import os.path
  import torch
  from torch_geometric.data import Data
  from torch_points3d.datasets.registration.base3dmatch import Base3DMatch
  from torch_points3d.datasets.registration.utils import PatchExtractor
  from torch_points3d.datasets.registration.utils import tracked_matches
  from torch_points3d.datasets.registration.pair import Pair, MultiScalePair
  from torch_points3d.metrics.registration_tracker import PatchRegistrationTracker
  from torch_points3d.metrics.registration_tracker import FragmentRegistrationTracker
  from torch_points3d.datasets.registration.base_siamese_dataset import BaseSiameseDataset
  from torch_points3d.datasets.registration.base_siamese_dataset import GeneralFragment
  from torch_points3d.datasets.registration.utils import compute_overlap_and_matches
  from torch_points3d.datasets.registration.test3dmatch import TestPair3DMatch
label_desc: Use image node_id 5 for calling the Patch3DMatch obj's underlying member method code with example usage: obj.__len__() and returns: size_dataset