class_docstr: Adds the dialogue sentence to the input (language modeling version).
  
  Language modeling version where a random piece of the label is sampled in
  the input. The rest is placed inside special tokens.
  
  E.g. run with: parlai display_data -t wizard_of_wikipedia -n 100 -dt valid --mutators
  flatten,add_label_to_input_lm_wow
  
  To add the checked sentence as the label, use:
      parlai display_data -t wizard_of_wikipedia -n 100 -dt valid --mutators
      flatten,add_label_to_input_lm_wow,checked_sentence_as_label_wow
class_docstr_tok: ["Adds","the","dialogue","sentence","to","the","input","(","language","modeling","version",")",".","Language","modeling","version","where","a","random","piece","of","the","label","is","sampled","in","the","input",".","The","rest","is","placed","inside","special","tokens",".","E.g",".","run","with",":","parlai","display_data","-t","wizard_of_wikipedia","-n","100","-dt","valid","--","mutators","flatten",",","add_label_to_input_lm_wow","To","add","the","checked","sentence","as","the","label",",","use",":","parlai","display_data","-t","wizard_of_wikipedia","-n","100","-dt","valid","--","mutators","flatten",",","add_label_to_input_lm_wow",",","checked_sentence_as_label_wow"]
code: def message_mutation(self, message: Message) -> Message:
      new_message = message.copy()
      if (
          "text" not in message
          or "labels" not in message
          or not message["labels"]
      ):
          return message
      if "dialogue_response" in new_message:
          # checked_sentence_as_label was applied before
          labels = new_message["dialogue_response"]
      else:
          labels = new_message["labels"]
      dialogue_response = labels[0]
      text = new_message.pop("text")
  
      ls = dialogue_response.split()
      ind = random.randint(0, len(ls) - 1)
      label1 = " ".join(ls[0:ind])
      label2 = " ".join(ls[ind : len(ls)])
  
      text += f"\n{label1}\n{CONST.TOKEN_LABEL} {label2} {CONST.TOKEN_END_LABEL}"
      new_message["text"] = text
  
      return new_message
  
imports: from parlai.core.mutators import register_mutator, MessageMutator, ManyEpisodeMutator
  from parlai.core.message import Message
  import parlai.tasks.wizard_of_internet.constants
  import random
label_desc: Use image node_id 1 for calling the AddLabelLM obj's underlying member method code with example usage: obj.message_mutation(message) and returns: new_message, message