code: def _setup_data(self, fold):
      self.data = []
      fpath = os.path.join(
          self.opt["datapath"], "Ubuntu", fold + ".csv"
      )
      print("loading: " + fpath)
      with PathManager.open(fpath, "r", newline="") as read:
          csv_read = csv.reader(read)
          next(csv_read)  # eat header
  
          for line in csv_read:
              fields = line[0].strip().split("__eou__ __eot__")
              fields.append(line[1].strip())
              dialog = []
              for field in fields:
                  if field != "":
                      dialog.append(
                          field.replace("__eou__", ".").strip()
                      )
              if len(dialog) > 2:
                  self.data.append(dialog)
  
imports: from parlai.core.teachers import DialogTeacher, FixedDialogTeacher
  from parlai.utils.io import PathManager
  from .build import build
  import csv
  import random
  import os
label_desc: Use image node_id 4 for calling the MultiturnTeacher obj's underlying member method code with example usage: obj._setup_data(fold) without return types