code: def __len__(self):
      return self.num_samples
  
file_path: ClassyVision/test/dataloader_async_gpu_wrapper_test.py
imports: import unittest
  import numpy
  import torch
  import torchvision.transforms
  from classy_vision.dataset.dataloader_async_gpu_wrapper import DataloaderAsyncGPUWrapper
  from PIL import Image
  from torch.utils.data import DataLoader, Dataset
label_desc: Use image node_id 4 for calling the ZeroImageDataset obj's underlying member method code with example usage: obj.__len__() and returns: self