code: def __len__(self):
      return self.n_samples
  
imports: from ctypes import pointer
  from tempfile import NamedTemporaryFile
  from collections import defaultdict
  from assertpy.assertpy import assert_that
  from multiprocessing import cpu_count
  import torch
  from assertpy import assert_that
  import numpy
  from torch.utils.data import Dataset
  from ffcv import DatasetWriter
  from ffcv.fields import IntField, NDArrayField, TorchTensorField
  from ffcv import Loader
label_desc: Use image node_id 2 for calling the DummyActivationsDataset obj's underlying member method code with example usage: obj.__len__() and returns: self