code: def setup_data(self, datafile):
      conversations = defaultdict(list)
  
      with jsonlines.open(datafile) as reader:
          for utterance in reader:
              text = utterance["text"]
              speaker = utterance["speaker"]
              conversation_id = utterance["conversation_id"]
  
              conversations[conversation_id].append(
                  {"text": text, "speaker": speaker}
              )
  
      for conversation_id in conversations:
          utterances = conversations[conversation_id]
          characters = set(
              [
                  u["speaker"]
                  for u in utterances
                  if u["speaker"] in self.characters
              ]
          )
          characters_string = ",".join(
              sorted(list(characters))
          )  # sorted to ensure same order across runs
          last_utterance_index = len(utterances) - 1
          speakers = []
  
          for index, utterance in enumerate(utterances):
              if index == 0:
                  if self.use_start_token:
                      context = self.start_token
  
                  else:  # skip the first utterance since there's no context
                      speaker = utterance["speaker"]
                      speakers.append(speaker)
  
                      text = self._get_text(utterance)
                      if self.include_speaker_in_context:
                          context = f"{speaker}: {text}"
                      else:
                          context = text
                      continue
  
              speaker = utterance["speaker"]
  
              text = self._get_text(utterance)
              prev_context = context
              if self.include_speaker_in_context:
                  context += (
                      self.utterance_delimiter + f"{speaker}: {text}"
                  )
              else:
                  context += self.utterance_delimiter + text
  
              isConversationDone = index == last_utterance_index
  
              # By default, generate training examples for all 6 main characters.
              # Otherwise only generate training examples for the chosen character.
              if (
                  self.character == "All" and speaker in self.characters
              ) or speaker == self.character:
                  (
                      text,
                      label,
                      speakers,
                      hasAddedSpeaker,
                  ) = self._get_message_fields(
                      text, speaker, speakers, prev_context
                  )
                  _speakers = speakers[:]
                  if not hasAddedSpeaker:
                      speakers.append(speaker)
                  yield {
                      "text": text,
                      "label": label,
                      "characters": characters_string,
                      "speakers": _speakers,
                  }, isConversationDone
              elif random.random() > self.silence_token_dropout:
                  (
                      text,
                      label,
                      speakers,
                      hasAddedSpeaker,
                  ) = self._get_message_fields(
                      self.silence_token,
                      self.character,
                      speakers,
                      prev_context,
                  )
                  _speakers = speakers[:]
                  if not hasAddedSpeaker:
                      speakers.append(speaker)
                  yield {
                      "text": text,
                      "label": label,
                      "characters": characters_string,
                      "speakers": _speakers,
                  }, isConversationDone
              else:
                  speakers.append(speaker)
  
imports: from typing import Optional
  from parlai.core.opt import Opt
  from parlai.core.teachers import DialogTeacher
  from parlai.core.params import ParlaiParser
  from .build import build
  from collections import defaultdict
  import jsonlines
  from parlai.utils.data import DatatypeHelper
  import random
  import copy
  import os
label_desc: Use image node_id 2 for calling the DefaultTeacher obj's underlying member method code with example usage: obj.setup_data(datafile) without return types