Optional[X] is equivalent to Union[X, None].
(self, parameters)
| 742 | |
| 743 | @_SpecialForm |
| 744 | def Optional(self, parameters): |
| 745 | """Optional[X] is equivalent to Union[X, None].""" |
| 746 | arg = _type_check(parameters, f"{self} requires a single type.") |
| 747 | return Union[arg, type(None)] |
| 748 | |
| 749 | @_TypedCacheSpecialForm |
| 750 | @_tp_cache(typed=True) |