code: def _get_indexable_sentences(document):
          
  
          def unroll_lists(list_of_lists):
              for i in itertools.product(*[set(j) for j in list_of_lists]):
                  yield ' '.join(i)
  
          sents = document.split_by_sentences()
          for order, sent in enumerate(sents):
              postags = list(unroll_lists(sent.postag_lists))
              lemmas = list(unroll_lists(sent.lemma_lists))
              text = sent.text
              words = copy.deepcopy(sent.words)
              for i in words:
                  del i['start']
                  del i['end']
  
              sentence = {
                  'estnltk_text_object': json.dumps(sent),
                  'meta': {
                      'order_in_parent': order
                  },
                  'text': text,
                  'words': words,
                  'postags': postags,
                  'lemmas': lemmas
              }
              yield json.dumps(sentence)
docs: Parameters
          ----------
          document : Text
              Article, book, paragraph, chapter, etc. Anything that is considered a document on its own.
  
         Yields
         ------
         str
              json representation of elasticsearch type sentence