class_docstr: Data preprocessor.
      
code: def __len__(self):
      return len(self.lst)
  
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 2 for calling the Dataset obj's underlying member method code with example usage: obj.__len__() and returns: len