code: def _add_opt_argument(self, opt_args, arg_parser):
          
          option_args = opt_args.copy()
  
          groups = option_args.pop('groups', None)
          if groups:
              self._add_group(
                  parser=arg_parser,
                  groups=groups,
                  option_args=option_args
              )
  
          exclusive_args = option_args.pop('mutually_exclusive', None)
          if exclusive_args:
              self._add_mutually_exclusive_group(
                  parser=arg_parser,
                  groups=exclusive_args,
                  option_args=option_args
              )
  
          for k, v in option_args.items():
              self._add_arg(parser=arg_parser, value_dict=v)
docs: Add an argument to an instantiated parser.
  
          :param opt_args: ``dict``
          :param arg_parser: ``object``