code: def __len__(self):
      return len(self.data)
  
imports: import math
  from PIL import Image
  import numpy
  import torch
  import torch.nn
  import torch.nn.functional
  import torchvision.transforms
  from torch.utils.data import Dataset, DataLoader
  from art.estimators.classification import PyTorchClassifier
  from art.data_generators import PyTorchDataGenerator
  from art.defences.trainer import AdversarialTrainerFBFPyTorch
  from art.utils import load_cifar10
  from art.attacks.evasion import ProjectedGradientDescent
label_desc: Use image node_id 3 for calling the CIFAR10_dataset obj's underlying member method code with example usage: obj.__len__() and returns: len