docs: def cleanup_after_optimize(filename, new_filename, old_format, new_format):
      """
      Replace old file with better one or discard new wasteful file.
  
      And report results using the stats module.
      """
      final_filename, bytes_in, bytes_out = _cleanup_after_optimize_aux(
          filename, new_filename, old_format, new_format)
      return stats.ReportStats(final_filename, bytes_count=(bytes_in, bytes_out))