code: def format_option_strings(self, option):
          
          if option.takes_value():
              metavar = option.metavar or option.dest.upper()
              short_opts = [self._short_opt_fmt % (sopt, metavar)
                            for sopt in option._short_opts]
              long_opts = [self._long_opt_fmt % (lopt, metavar)
                           for lopt in option._long_opts]
          else:
              short_opts = option._short_opts
              long_opts = option._long_opts
  
          if self.short_first:
              opts = short_opts + long_opts
          else:
              opts = long_opts + short_opts
  
          return ", ".join(opts)
docs: Return a comma-separated list of option strings & metavariables.