docs: def excise(self, ngram):
          """Removes all rows whose n-gram contains `ngram`.
  
          This operation uses simple string containment matching. For
          tokens that consist of multiple characters, this means that
          `ngram` may be part of one or two tokens; eg, "he m" would
          match on "she may".
  
          :param ngram: n-gram to remove containing n-gram rows by
          :type ngram: `str`
  
          """
          self._logger.info('Excising results containing "{}"'.format(ngram))
          if not ngram:
              return
          self._matches = self._matches[~self._matches[
              constants.NGRAM_FIELDNAME].str.contains(ngram, regex=False)]