code: def __init__(self, length):
      self.length = length
      self.episodes = [3 * i % 5 + 1 for i in range(self.length)]
  
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 1 to create a new DummyDataset object from inherited base classes: Dataset with example: obj = DummyDataset(length)