docs: def list_styles(self):
          """Print available styles and exit.
          """
          known = sorted(self.defaults.known_styles)
          if not known:
              err_exit('No styles', 0)
          for style in known:
              if style == self.defaults.default_style:
                  print(style, '(default)')
              else:
                  print(style)
          sys.exit(0)