code: def __len__(self):
      return self.len
  
file_path: dgl/examples/pytorch/TAHIN/data_loader.py
imports: import os
  import pickle
  import random
  import dgl
  import numpy
  import torch
  from torch.utils.data import DataLoader, Dataset
label_desc: Use image node_id 3 for calling the MyDataset obj's underlying member method code with example usage: obj.__len__() and returns: self