docs: def _generate_statistics(self, out_path, results_path):
          """Writes a statistics report for the results at `results_path` to
          `out_path`.
  
          Reuses an existing statistics report if one exists at
          `out_path`.
  
          :param out_path: path to output statistics report to
          :type out_path: `str`
          :param results_path: path of results to generate statistics for
          :type results_path: `str`
  
          """
          if not os.path.exists(out_path):
              report = StatisticsReport(self._corpus, self._tokenizer,
                                        results_path)
              report.generate_statistics()
              with open(out_path, mode='w', encoding='utf-8', newline='') as fh:
                  report.csv(fh)