Changed combine method in datetime to use aliased _date and _time types (like all other methods in this class) to avoid namespace collision with date and time methods. (#3251)

stdlib/2and3/datetime.pyi

@@ -233,10 +233,10 @@ class datetime(date):
     def utcnow(cls) -> datetime: ...
     if sys.version_info >= (3, 6):
         @classmethod
-        def combine(cls, date: date, time: time, tzinfo: Optional[_tzinfo] = ...) -> datetime: ...
+        def combine(cls, date: _date, time: _time, tzinfo: Optional[_tzinfo] = ...) -> datetime: ...
     else:
         @classmethod
-        def combine(cls, date: date, time: time) -> datetime: ...
+        def combine(cls, date: _date, time: _time) -> datetime: ...
     if sys.version_info >= (3, 7):
         @classmethod
         def fromisoformat(cls, date_string: str) -> datetime: ...