class_docstr: Mutator that throw away WoI gold doc fields so the OBSERVATION_ECHO_RETRIEVER
  doesn't return top_docs.
class_docstr_tok: ["Mutator","that","throw","away","WoI","gold","doc","fields","so","the","OBSERVATION_ECHO_RETRIEVER","does","n't","return","top_docs","."]
code: def message_mutation(self, message: Message) -> Message:
      new_message = copy.deepcopy(message)
      if message["labels"][0] == "__ok__":
          new_message.force_set("labels", ["pos"])
      elif message["labels"][0] == "__notok__":
          new_message.force_set("labels", ["neg"])
      return new_message
  
imports: from string import punctuation
  import copy
  from typing import List
  from parlai.core.mutators import register_mutator, ManyEpisodeMutator, MessageMutator
  from parlai.core.message import Message
  from parlai.mutators.flatten import FlattenMutator
  from parlai.utils.strings import normalize_reply
  from parlai.tasks.wizard_of_wikipedia.agents import TOKEN_KNOWLEDGE, TOKEN_END_KNOWLEDGE
  from parlai.tasks.wizard_of_internet import constants
  from .constants import FeedbackType, UNWANTED_TOKENS
label_desc: Use image node_id 1 for calling the PosNegLabelConvertor obj's underlying member method code with example usage: obj.message_mutation(message) and returns: new_message