class_docstr: A class implementing the chatbot problem for the OpenSubtitles dataset.
  
  http://opus.nlpl.eu/OpenSubtitles-v2018.php
class_docstr_tok: ["A","class","implementing","the","chatbot","problem","for","the","OpenSubtitles","dataset",".","http",":","\/\/opus.nlpl.eu\/OpenSubtitles-v2018.php"]
code: def dataset_version(self):
      # Year of the opensubtitles dataset creation.
      return 2009
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import collections
  import os
  import re
  import zipfile
  from tensor2tensor.data_generators import dialog_abstract
  from tensor2tensor.data_generators import text_encoder
  from tensor2tensor.utils import registry
label_desc: Use image node_id 2 for calling the DialogOpensubtitles64k2009 obj's underlying member method code with example usage: obj.dataset_version() and returns: int