class_docstr: Teacher which contains the question as the text, the sentences as the label
  candidates, and the label as the sentence containing the answer.
  
  Some punctuation may be removed for tokenization purposes.
class_docstr_tok: ["Teacher","which","contains","the","question","as","the","text",",","the","sentences","as","the","label","candidates",",","and","the","label","as","the","sentence","containing","the","answer",".","Some","punctuation","may","be","removed","for","tokenization","purposes","."]
code: def get(self, episode_idx, entry_idx=None):
      article_idx, paragraph_idx, qa_idx = self.examples[episode_idx]
      article = self.squad[article_idx]
      paragraph = article["paragraphs"][paragraph_idx]
      qa = paragraph["qas"][qa_idx]
      context = paragraph["context"]
      question = qa["question"]
  
      answers = [""]
      if not qa["is_impossible"]:
          answers = [a["text"] for a in qa["answers"]]
  
      # remove '.', '?', '!' from answers for proper sentence
      # tokenization
      edited_answers = []
      for answer in answers:
          new_answer = (
              answer.replace(".", "").replace("?", "").replace("!", "")
          )
          context = context.replace(answer, new_answer)
          edited_answers.append(new_answer)
  
      edited_sentences = self.sent_tok.tokenize(context)
  
      labels = []
      for sentence in edited_sentences:
          for answer in edited_answers:
              if answer in sentence and sentence not in labels:
                  labels.append(sentence)
                  break
  
      plausible = []
      if qa["is_impossible"]:
          plausible = qa["plausible_answers"]
          labels = [self.opt["impossible_answer_string"]]
      action = {
          "id": "SquadSentenceLabels",
          "text": question,
          "labels": labels,
          "plausible_answers": plausible,
          "label_candidates": edited_sentences,
          "episode_done": True,
      }
  
      return action
  
imports: from typing import Optional
  from parlai.core.params import ParlaiParser
  from parlai.core.opt import Opt
  from parlai.core.teachers import FixedDialogTeacher, DialogTeacher
  from parlai.utils.io import PathManager
  from .build import build
  import json
  import os
label_desc: Use image node_id 2 for calling the SentenceLabelsTeacher obj's underlying member method code with example usage: obj.get(episode_idx, entry_idx) and returns: action