class_docstr: Replaces the episode labels in messages with "personal_knwowledge".
  
  Episodes are flattened to ensure dialogue history is maintained appropriately.
code: def many_episode_mutation(
      self, episode: List[Message]
  ) -> List[List[Message]]:
      history = []
      for message in episode:
          if message["text"] == "__SILENCE__":
              continue
          history.append(message.pop("text"))
          message["text"] = "\n".join(history)
          labels = message.pop("labels")
          message["labels"] = ["personal_knowledge"]
          yield [message]
          history.append(random.choice(labels))
  
imports: import random
  from typing import List
  from parlai.core.message import Message
  from parlai.core.mutators import register_mutator, ManyEpisodeMutator
label_desc: Use image node_id 1 for calling the LongTermMemoryMutator obj's underlying member method code with example usage: obj.many_episode_mutation(episode) without return types