Made BaseContext __setitem__ and __getitem__ consistant. (#1040)

* Made BaseContext __setitem__ and __getitem__ consistant.

* Standardised ContextKeys

django-stubs/template/context.pyi

@@ -6,6 +6,7 @@ from django.template.base import Node, Origin, Template
 from django.template.defaulttags import IfChangedNode
 from django.template.loader_tags import IncludeNode
 
+_ContextKeys = Union[int, str, Node]
 _ContextValues = Union[Dict[str, Any], "Context"]
 _ContextCopy = TypeVar("_ContextCopy", bound="BaseContext")
 
@@ -23,17 +24,17 @@ class BaseContext(Iterable[Any]):
     def __iter__(self) -> Iterator[Any]: ...
     def push(self, *args: Any, **kwargs: Any) -> ContextDict: ...
     def pop(self) -> ContextDict: ...
-    def __setitem__(self, key: Union[Node, str], value: Any) -> None: ...
-    def set_upward(self, key: str, value: Union[int, str]) -> None: ...
-    def __getitem__(self, key: Union[int, str]) -> Any: ...
-    def __delitem__(self, key: Any) -> None: ...
-    def __contains__(self, key: str) -> bool: ...
-    def get(self, key: str, otherwise: Optional[Any] = ...) -> Optional[Any]: ...
+    def __setitem__(self, key: _ContextKeys, value: Any) -> None: ...
+    def set_upward(self, key: _ContextKeys, value: Union[int, str]) -> None: ...
+    def __getitem__(self, key: _ContextKeys) -> Any: ...
+    def __delitem__(self, key: _ContextKeys) -> None: ...
+    def __contains__(self, key: _ContextKeys) -> bool: ...
+    def get(self, key: _ContextKeys, otherwise: Optional[Any] = ...) -> Optional[Any]: ...
     def setdefault(
-        self, key: Union[IfChangedNode, str], default: Optional[Union[List[Origin], int]] = ...
+        self, key: _ContextKeys, default: Optional[Union[List[Origin], int]] = ...
     ) -> Optional[Union[List[Origin], int]]: ...
     def new(self, values: Optional[_ContextValues] = ...) -> Context: ...
-    def flatten(self) -> Dict[str, Optional[Union[Dict[str, Union[Type[Any], str]], int, str]]]: ...
+    def flatten(self) -> Dict[_ContextKeys, Optional[Union[Dict[_ContextKeys, Union[Type[Any], str]], int, str]]]: ...
 
 class Context(BaseContext):
     dicts: Any