Merge pull request #494 from hcarty/typing-override-typeisguard

Add typing.(override, TypeIs, TypeGuard)

python/typing.py

@@ -50,6 +50,7 @@ TYPE_CHECKING = False
 
 # decorators
 overload = lambda x: x
+override = lambda x: x
 final = lambda x: x
 
 # exhaustiveness checking
@@ -59,5 +60,7 @@ TypedDict = dict
 NotRequired = _PLACEHOLDER
 ReadOnly = _PLACEHOLDER
 Required = _PLACEHOLDER
+TypeIs = _PLACEHOLDER
+TypeGuard = _PLACEHOLDER
 
 cast = lambda _, val: val