code: def get_data_for_fold(self, fold):
      extrinsic_step = self.opt.get("extrinsic_step", False)
      data_file, version = super().get_datafile()
  
      process_funcs = {
          "base": self.process_base,
          "stage": self.process_stage,
          "abduct": self.process_abduct,
      }
  
      messages = []
      with PathManager.open(data_file) as f:
          for x in f.readlines():
              for ex in process_funcs[version](json.loads(x.strip())):
                  # include only datapoint with at least 1 step
                  if len(ex[0]["steps"]) > 0:
                      messages.append(
                          {
                              "question": ex[0]["text"],
                              "answer": ex[0]["label"],
                              "steps": ex[0]["steps"],
                          }
                      )
  
      for m in messages:
          if extrinsic_step:
              random_step = None
              # make sure new step is from a different context
              # here we aasume that there is at least one step in the set
              # with different context, otherwise it will go in the
              # infinite loop
              while not random_step or random_step in m["question"]:
                  rand_steps = self.proofwriter_random.choice(messages)[
                      "steps"
                  ]
                  random_step = self.proofwriter_random.choice(
                      rand_steps
                  )
              m["extrinsic_step"] = random_step
              yield m
          else:
              yield m
  
imports: import json
  import os
  import copy
  import random
  import re
  from typing import Optional, List, Tuple
  from tasks.reasoning.agents import StepByStepReasoningTeacher
  from .build import build
  from parlai.core.message import Message
  from parlai.core.mutators import ManyEpisodeMutator, register_mutator
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.teachers import DialogTeacher
  from parlai.utils.data import DatatypeHelper
  from parlai.utils.io import PathManager
label_desc: Use image node_id 3 for calling the ProofWriterStepByStepReasoningTeacher obj's underlying member method code with example usage: obj.get_data_for_fold(fold) without return types