docs: def prune_by_ngram(self, ngrams):
          """Removes results rows whose n-gram is in `ngrams`.
  
          :param ngrams: n-grams to remove
          :type ngrams: `list` of `str`
  
          """
          self._logger.info('Pruning results by n-gram')
          self._matches = self._matches[
              ~self._matches[constants.NGRAM_FIELDNAME].isin(ngrams)]