code: def __len__(self):
      return self.x.shape[0]
  
imports: import os
  from unittest import TestCase
  import numpy
  import pytest
  import torch
  import torch.nn
  from torch.utils.data import Dataset, DataLoader
  from bigdl.orca.automl.auto_estimator import AutoEstimator
  from bigdl.orca.automl.pytorch_utils import LR_NAME
  from bigdl.orca.automl import hp
label_desc: Use image node_id 2 for calling the CustomDataset obj's underlying member method code with example usage: obj.__len__() and returns: self