docs: def optimize_image(arg):
      """Optimize a given image from a filename."""
      try:
          filename, image_format, settings = arg
  
          Settings.update(settings)
  
          format_module, nag_about_gifs = _get_format_module(image_format)
  
          if format_module is None:
              if Settings.verbose > 1:
                  print(filename, image_format)  # image.mode)
                  print("\tFile format not selected.")
              return None
  
          report_stats = _optimize_with_progs(format_module, filename,
                                              image_format)
          report_stats.nag_about_gifs = nag_about_gifs
          stats.report_saved(report_stats)
          return report_stats
      except Exception as exc:
          print(exc)
          traceback.print_exc()
          return stats.ReportStats(filename, error="Optimizing Image")