class_docstr: Filter examples by last feedback, by subclassing FlattenMutator it is equivalent to.
  
  --mutators flatten+<this_mutator>
class_docstr_tok: ["Filter","examples","by","last","feedback",",","by","subclassing","FlattenMutator","it","is","equivalent","to",".","--","mutators","flatten+","<","this_mutator",">"]
code: def many_episode_mutation(self, episode):
      episodes = super().many_episode_mutation(episode)
      for episode in episodes:
          if (
              episode[-1]["last_nonperfect_feedback"]
              == self.target_feedback
          ):
              yield 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 FeedbackMixin obj's underlying member method code with example usage: obj.many_episode_mutation(episode) without return types