class_docstr: Teacher that corresponds to the default DSTC7 ubuntu track 1.
  
  The data hasn't been augmented by using the multi-turn utterances.
code: def get(self, episode_idx, entry_idx=0):
      rand = random.Random(episode_idx)
      episode = self.data[episode_idx]
      texts = []
      for m in episode["messages-so-far"]:
          texts.append(m["speaker"].replace("_", " ") + ": ")
          texts.append(m["utterance"] + "\n")
      text = "".join(texts)
      labels = [
          m["utterance"] for m in episode["options-for-correct-answers"]
      ]
      candidates = [m["utterance"] for m in episode["options-for-next"]]
      if labels[0] not in candidates:
          candidates = labels + candidates
      rand.shuffle(candidates)
      label_key = "labels" if self.split == "train" else "eval_labels"
      return {
          "text": text,
          label_key: labels,
          "label_candidates": candidates,
          "episode_done": True,
      }
  
imports: from parlai.core.teachers import FixedDialogTeacher
  from parlai.utils.io import PathManager
  from .build import build
  import json
  import os
  import random
label_desc: Use image node_id 6 for calling the DSTC7Teacher obj's underlying member method code with example usage: obj.get(episode_idx, entry_idx) and returns: dict