class_docstr: Mutator that provides self character in a special observation field.
code: def episode_mutation(self, episode: List[Message]) -> List[Message]:
      characters = extract_characters(episode[0]["text"])
      for ep in episode:
          ep.force_set("self_character", characters["_self_name"])
      return 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 ShareSelfCharacterMutator obj's underlying member method code with example usage: obj.episode_mutation(episode) and returns: episode