class_docstr: Mutator that breaks down episodes into all partial sequences (Left To Right).
code: def many_episode_mutation(
      self, episode: List[Message]
  ) -> List[Message]:
      new_episodes = []
      for message in episode:
          label_words = message["labels"][0].split()
          if len(label_words) < 2:
              continue
          for i in range(1, len(label_words) + 1):
              new_message = message.copy()
              label = " ".join(label_words[:i])
              new_message.force_set("labels", [label])
              new_episodes.append([new_message])
      return new_episodes
  
imports: from typing import List, Tuple
  from typing import Optional
  from parlai.core.agents import Agent, create_agent_from_model_file, create_agent_from_shared
  from parlai.core.params import ParlaiParser
  from parlai.core.message import Message
  from parlai.core.opt import Opt
  from parlai.core.mutators import register_mutator, ManyEpisodeMutator, EpisodeMutator
  import parlai.tasks.bot_adversarial_dialogue.agents
  import parlai.tasks.dialogue_safety.agents
  import parlai.utils.logging
  from parlai.core.metrics import AverageMetric
label_desc: Use image node_id 1 for calling the LeftToRightMutator obj's underlying member method code with example usage: obj.many_episode_mutation(episode) and returns: new_episodes