Type asc/desc operators (#122)

Author: isra17

sqlalchemy-stubs/sql/operators.pyi

@@ -1,6 +1,6 @@
 from typing import Any, Optional, Text, List, Union
 from .selectable import Select as Select
-from .elements import BindParameter as BindParameter
+from .elements import BindParameter as BindParameter, UnaryExpression
 
 class Operators(object):
     def __and__(self, other): ...
@@ -52,8 +52,8 @@ class ColumnOperators(Operators):
     def endswith(self, other, **kwargs): ...
     def contains(self, other, **kwargs): ...
     def match(self, other, **kwargs): ...
-    def desc(self): ...
-    def asc(self): ...
+    def desc(self) -> UnaryExpression: ...
+    def asc(self) -> UnaryExpression: ...
     def nullsfirst(self): ...
     def nullslast(self): ...
     def collate(self, collation): ...