code: def __len__(self):
      return self.num_episodes
  
file_path: ReAgent/reagent/gym/datasets/episodic_dataset.py
imports: import logging
  from typing import Optional
  import torch
  from reagent.gym.agents.agent import Agent
  from reagent.gym.envs.gym import Gym
  from reagent.gym.runners.gymrunner import run_episode
label_desc: Use image node_id 3 for calling the EpisodicDataset obj's underlying member method code with example usage: obj.__len__() and returns: self