class_docstr: give gold knowledge as target w/o special tokens.
class_docstr_tok: ["give","gold","knowledge","as","target","w\/o","special","tokens","."]
code: def many_episode_mutation(self, episode):
      episodes = super().many_episode_mutation(episode)
      for episode in episodes:
          assert len(episode) == 1
          if "selected_sentences" in episode[-1]:
              new_episode = copy.deepcopy(episode)
              new_episode[-1].force_set(
                  "labels",
                  [normalize_reply(episode[-1]["selected_sentences"])],
              )
              yield new_episode
  
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 GoldKnowledgeNoSpecialToken obj's underlying member method code with example usage: obj.many_episode_mutation(episode) without return types