Add test case for Provider.provider type propagation

Author: ZipFile

tests/typing/provider.py

@@ -4,6 +4,7 @@
 # Test 1: to check .provided attribute
 provider1: providers.Provider[int] = providers.Object(1)
 provided: int = provider1.provided()
+provider1_delegate: providers.Provider[int] = provider1.provider
 
 # Test 2: to check async mode API
 provider2: providers.Provider = providers.Provider()