code: def __getitem__(self, index):
      assert 0 <= index < self.length
      return index, self.episodes[index]
  
imports: from collections import Counter
  import gym
  import numpy
  from tianshou.data import Batch, Collector
  from tianshou.policy import BasePolicy
  from torch.utils.data import DataLoader, Dataset, DistributedSampler
  from qlib.rl.utils.finite_env import LogWriter, FiniteDummyVectorEnv, FiniteShmemVectorEnv, FiniteSubprocVectorEnv, check_nan_observation, generate_nan_observation
label_desc: Use image node_id 2 for calling the DummyDataset obj's underlying member method code with example usage: obj.__getitem__(index) and returns: index,  self