Add test to import all modules to check validity of stubs (#56)

* add import_all.test builder

* fix errors

* fix typechecking errors

* fix migrations typechecking

django-stubs/template/base.pyi

@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Any, Callable, Dict, Iterator, List, Mapping, Optional, Tuple, Type, Union
+from typing import Any, Callable, Dict, Iterator, List, Mapping, Optional, Sequence, Tuple, Type, Union
 
 from django.http.request import HttpRequest
 from django.template.context import Context as Context
@@ -126,12 +126,12 @@ filter_re: Any
 
 class FilterExpression:
     token: str = ...
-    filters: List[Tuple[Callable, List[Tuple[bool, Union[Variable, SafeText]]]]] = ...
-    var: Union[Variable, SafeText] = ...
+    filters: List[Any] = ...
+    var: Any = ...
     def __init__(self, token: str, parser: Parser) -> None: ...
-    def resolve(self, context: Union[Dict[str, Dict[str, str]], Context], ignore_failures: bool = ...) -> Any: ...
+    def resolve(self, context: Mapping[str, Any], ignore_failures: bool = ...) -> Any: ...
     @staticmethod
-    def args_check(name: str, func: Callable, provided: List[Tuple[bool, Union[Variable, SafeText]]]) -> bool: ...
+    def args_check(name: str, func: Callable, provided: List[Tuple[bool, Any]]) -> bool: ...
 
 class Variable:
     var: Union[Dict[Any, Any], str] = ...
@@ -152,27 +152,21 @@ class Node:
     def __iter__(self) -> None: ...
     def get_nodes_by_type(self, nodetype: Type[Node]) -> List[Node]: ...
 
-class NodeList(list):
+class NodeList(List[Node]):
     contains_nontext: bool = ...
     def render(self, context: Context) -> SafeText: ...
     def get_nodes_by_type(self, nodetype: Type[Node]) -> List[Node]: ...
 
 class TextNode(Node):
-    origin: Origin
-    token: Token
     s: str = ...
     def __init__(self, s: str) -> None: ...
-    def render(self, context: Context) -> str: ...
 
 def render_value_in_context(value: Any, context: Context) -> str: ...
 
 class VariableNode(Node):
-    origin: Origin
-    token: Token
     filter_expression: FilterExpression = ...
     def __init__(self, filter_expression: FilterExpression) -> None: ...
-    def render(self, context: Context) -> str: ...
 
 kwarg_re: Any
 
-def token_kwargs(bits: List[str], parser: Parser, support_legacy: bool = ...) -> Dict[str, FilterExpression]: ...
+def token_kwargs(bits: Sequence[str], parser: Parser, support_legacy: bool = ...) -> Dict[str, FilterExpression]: ...