docs: def diff_supplied(self, results_filenames, labels, tokenizer, output_fh):
          """Returns `output_fh` populated with CSV results giving the n-grams
          that are unique to the witnesses in each set of works in
          `results_sets`, using the labels in `labels`.
  
          Note that this is not the same as the symmetric difference of
          these sets, except in the case where there are only two
          labels.
  
          :param results_filenames: list of results filenames to be diffed
          :type results_filenames: `list` of `str`
          :param labels: labels to be applied to the results_sets
          :type labels: `list`
          :param tokenizer: tokenizer for the n-grams
          :type tokenizer: `Tokenizer`
          :param output_fh: object to output results to
          :type output_fh: file-like object
          :rtype: file-like object
  
          """
          self._add_temporary_results_sets(results_filenames, labels)
          query = constants.SELECT_DIFF_SUPPLIED_SQL
          self._logger.info('Running supplied diff query')
          self._logger.debug('Query: {}'.format(query))
          self._log_query_plan(query, [])
          cursor = self._conn.execute(query)
          return self._diff(cursor, tokenizer, output_fh)