docs: def _is_intersect_results(results):
          """Returns False if `results` has an n-gram that exists in only one
          label, True otherwise.
  
          :param results: results to analyze
          :type results: `pandas.DataFrame`
          :rtype: `bool`
  
          """
          sample = results.iloc[0]
          ngram = sample[constants.NGRAM_FIELDNAME]
          label = sample[constants.LABEL_FIELDNAME]
          return not(results[
              (results[constants.NGRAM_FIELDNAME] == ngram) &
              (results[constants.LABEL_FIELDNAME] != label)].empty)