class_docstr: Mutator that breaks down episodes into all partial sequences.
code: def episode_mutation(self, episode: List[Message]) -> List[Message]:
      new_episode = []
      for ep in episode:
          label_words = ep.pop("labels")[0].split()
          for i in range(1, len(label_words) + 1):
              new_episode.append(
                  Message({**ep, "labels": [" ".join(label_words[:i])]})
              )
      return new_episode
  
file_path: ParlAI/projects/light_whoami/task/mutators.py
imports: import re
  from parlai.core.message import Message
  from parlai.core.mutators import register_mutator, EpisodeMutator
  from typing import List
  from projects.light_whoami.task.utils import DEFAULT_DELIM, CONTEXT_KEYS, extract_characters
label_desc: Use image node_id 1 for calling the LeftToRightMutator obj's underlying member method code with example usage: obj.episode_mutation(episode) and returns: new_episode