code: def add_argument(self, dest, nargs=1, obj=None):
          
          if obj is None:
              obj = dest
          self._args.append(Argument(dest=dest, nargs=nargs, obj=obj))
docs: Adds a positional argument named `dest` to the parser.
  
          The `obj` can be used to identify the option in the order list
          that is returned from the parser.