code: def n_episodes(self):
      return len(self.episodic_memory)
  
file_path: chainerrl/chainerrl/replay_buffers/episodic.py
imports: import collections
  import pickle
  from chainerrl.misc.collections import RandomAccessQueue
  from chainerrl.replay_buffer import AbstractEpisodicReplayBuffer
  from chainerrl.replay_buffer import random_subseq
label_desc: Use image node_id 6 for calling the EpisodicReplayBuffer obj's underlying member method code with example usage: obj.n_episodes() and returns: len