docs: def _add_text_size_ngrams(self, text_id, size, ngrams):
          """Adds `ngrams`, that are of size `size`, to the data store.
  
          The added `ngrams` are associated with `text_id`.
  
          :param text_id: database ID of text associated with `ngrams`
          :type text_id: `int`
          :param size: size of n-grams
          :type size: `int`
          :param ngrams: n-grams to be added
          :type ngrams: `collections.Counter`
  
          """
          unique_ngrams = len(ngrams)
          self._logger.info('Adding {} unique {}-grams'.format(
              unique_ngrams, size))
          parameters = [[text_id, ngram, size, count]
                        for ngram, count in ngrams.items()]
          with self._conn:
              self._conn.execute(constants.INSERT_TEXT_HAS_NGRAM_SQL,
                                 [text_id, size, unique_ngrams])
              self._conn.executemany(constants.INSERT_NGRAM_SQL, parameters)