class_docstr: Data preprocessor.
      
code: def get(self, idx):
      idx, start, end = self.lst[idx]
      source = self.raw[idx][start : end - 1]
      target = self.raw[idx][end - 1]
      source = " ".join([b for a, b, c in source])
      cct = self.raw[idx][end - 2][0] == self.raw[idx][end - 1][0]
      return self.topics[idx], cct, source, target
  
file_path: texar/examples/hierarchical_dialog/sw_loader.py
imports: import os
  import json
  from json_lines import reader
  from nltk.tokenize import WordPunctTokenizer
  from sklearn.feature_extraction.text import TfidfVectorizer
  import texar.tf
  from config_data import data_root
label_desc: Use image node_id 4 for calling the Dataset obj's underlying member method code with example usage: obj.get(idx) and returns: self,  cct,  source,  target