code: def __len__(self):
      return 100
  
file_path: baal/tests/ensemble_test.py
imports: import pytest
  import torch
  from torch import nn
  from torch import optim
  from torch.utils.data import Dataset
  from baal.ensemble import EnsembleModelWrapper, ensemble_prediction
label_desc: Use image node_id 1 for calling the DummyDataset obj's underlying member method code with example usage: obj.__len__() and returns: int