def _get_indexable_sentences(document):
        """
        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

        """

        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)
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