class_docstr: Allows to filter any examples where '__retrieved-docs__' field doesn't contain the
  '__selected-sentences__'.
code: def many_episode_mutation(self, episode):
      out_episodes = []
      for e in episode:
          checked_sentences = e.get(
              CONST.SELECTED_SENTENCES,
              e.get("labels", [CONST.NO_SELECTED_SENTENCES_TOKEN]),
          )
          docs = " ".join(e.get("__retrieved-docs__"))
          if (
              " ".join(checked_sentences)
              != CONST.NO_SELECTED_SENTENCES_TOKEN
          ):
              found = True
              for sent in checked_sentences:
                  s = sent.lstrip(" ").rstrip(" ")
                  if s not in docs:
                      found = False
              if found:
                  out_episodes.append([e])
          else:
              pass
      return out_episodes
  
imports: import torch
  from parlai.core.mutators import register_mutator, MessageMutator, ManyEpisodeMutator
  from typing import Optional
  from parlai.core.opt import Opt
  from parlai.core.message import Message
  from parlai.core.params import ParlaiParser
  import parlai.tasks.wizard_of_internet.constants
  from parlai.tasks.wizard_of_wikipedia.mutators import AddLabel, AddLabelLM, CheckedSentenceAsLabel, AddCheckedSentence
label_desc: Use image node_id 1 for calling the WoiFilterSelectedKnowledgeInRetrievedDocs obj's underlying member method code with example usage: obj.many_episode_mutation(episode) and returns: out_episodes