code: def __len__(self):
      return self.l
  
imports: import os
  from tempfile import NamedTemporaryFile
  from time import sleep, time
  import numpy
  from tqdm import tqdm
  from assertpy import assert_that
  from torch.utils.data import Dataset
  from ffcv.writer import DatasetWriter
  from ffcv.reader import Reader
  from ffcv.fields import BytesField, IntField
  from ffcv.pipeline.compiler import Compiler
  from ffcv.memory_managers import OSCacheManager
  from ffcv.libffcv import memcpy
  from ..decorator import benchmark
  from ..benchmark import Benchmark
label_desc: Use image node_id 2 for calling the DummyDataset obj's underlying member method code with example usage: obj.__len__() and returns: self