code: def _define_absl_flag(self, flag_instance, suppress):
      
      flag_name = flag_instance.name
      short_name = flag_instance.short_name
      argument_names = ['--' + flag_name]
      if short_name:
        argument_names.insert(0, '-' + short_name)
      if suppress:
        helptext = argparse.SUPPRESS
      else:
        # argparse help string uses %-formatting. Escape the literal %'s.
        helptext = flag_instance.help.replace('%', '%%')
      if flag_instance.boolean:
        # Only add the `no` form to the long name.
        argument_names.append('--no' + flag_name)
        self.add_argument(
            *argument_names, action=_BooleanFlagAction, help=helptext,
            metavar=flag_instance.name.upper(),
            flag_instance=flag_instance)
      else:
        self.add_argument(
            *argument_names, action=_FlagAction, help=helptext,
            metavar=flag_instance.name.upper(),
            flag_instance=flag_instance)
docs: Defines a flag from the flag_instance.