code: def __len__(self):
      return len(self.data)
  
imports: import json
  import os
  from zipfile import ZipFile
  import dgl
  import numpy
  import tqdm
  from dgl.data.utils import download, get_download_dir
  from scipy.sparse import csr_matrix
  from torch.utils.data import Dataset
label_desc: Use image node_id 3 for calling the ShapeNetDataset obj's underlying member method code with example usage: obj.__len__() and returns: len