code: def __len__(self):
      return self.num_samples
  
imports: import contextlib
  import logging
  import queue
  from typing import Dict, List
  import numpy
  import torch
  from PIL import Image
  from torch.utils.data import Dataset
  from torch.utils.data.distributed import DistributedSampler
label_desc: Use image node_id 13 for calling the StratifiedClassSampler obj's underlying member method code with example usage: obj.__len__() and returns: self