code: def sample_episodes(self, n_episodes, max_len=None):
      assert len(self.episodic_memory) >= n_episodes
      episodes = self.episodic_memory.sample(n_episodes)
      if max_len is not None:
          return [random_subseq(ep, max_len) for ep in episodes]
      else:
          return episodes
  
file_path: pfrl/pfrl/replay_buffers/episodic.py
imports: import collections
  import pickle
  from typing import Optional
  from pfrl.collections.random_access_queue import RandomAccessQueue
  from pfrl.replay_buffer import AbstractEpisodicReplayBuffer, random_subseq
label_desc: Use image node_id 4 for calling the EpisodicReplayBuffer obj's underlying member method code with example usage: obj.sample_episodes(n_episodes, max_len) and returns: unknown, episodes