Switch to black formatting in stubs

Also block isort from stubs -- it plays ping-pong with black about an empty
line after imports.

src/attr/__init__.pyi

@@ -24,7 +24,6 @@ from . import setters as setters
 from . import validators as validators
 from ._version_info import VersionInfo
 
-
 __version__: str
 __version_info__: VersionInfo
 __title__: str
@@ -49,7 +48,9 @@ _OnSetAttrType = Callable[[Any, Attribute[Any], Any], Any]
 _OnSetAttrArgType = Union[
     _OnSetAttrType, List[_OnSetAttrType], setters._NoOpType
 ]
-_FieldTransformer = Callable[[type, List[Attribute[Any]]], List[Attribute[Any]]]
+_FieldTransformer = Callable[
+    [type, List[Attribute[Any]]], List[Attribute[Any]]
+]
 # FIXME: in reality, if multiple validators are passed they must be in a list
 # or tuple, but those are invariant and so would prevent subtypes of
 # _ValidatorType from working when passed in a list or tuple.
@@ -64,7 +65,6 @@ NOTHING: object
 # Work around mypy issue #4554 in the common case by using an overload.
 if sys.version_info >= (3, 8):
     from typing import Literal
-
     @overload
     def Factory(factory: Callable[[], _T]) -> _T: ...
     @overload
@@ -77,6 +77,7 @@ if sys.version_info >= (3, 8):
         factory: Callable[[], _T],
         takes_self: Literal[False],
     ) -> _T: ...
+
 else:
     @overload
     def Factory(factory: Callable[[], _T]) -> _T: ...
@@ -117,7 +118,6 @@ class Attribute(Generic[_T]):
     type: Optional[Type[_T]]
     kw_only: bool
     on_setattr: _OnSetAttrType
-
     def evolve(self, **changes: Any) -> "Attribute[Any]": ...
 
 # NOTE: We had several choices for the annotation to use for type arg:
@@ -452,7 +452,9 @@ def asdict(
     filter: Optional[_FilterType[Any]] = ...,
     dict_factory: Type[Mapping[Any, Any]] = ...,
     retain_collection_types: bool = ...,
-    value_serializer: Optional[Callable[[type, Attribute[Any], Any], Any]] = ...,
+    value_serializer: Optional[
+        Callable[[type, Attribute[Any], Any], Any]
+    ] = ...,
 ) -> Dict[str, Any]: ...
 
 # TODO: add support for returning NamedTuple from the mypy plugin

src/attr/_cmp.pyi

@@ -2,7 +2,6 @@ from typing import Type
 
 from . import _CompareWithType
 
-
 def cmp_using(
     eq: Optional[_CompareWithType],
     lt: Optional[_CompareWithType],

src/attr/converters.pyi

@@ -2,7 +2,6 @@ from typing import Callable, Optional, TypeVar, overload
 
 from . import _ConverterType
 
-
 _T = TypeVar("_T")
 
 def pipe(*validators: _ConverterType) -> _ConverterType: ...

src/attr/exceptions.pyi

@@ -1,6 +1,5 @@
 from typing import Any
 
-
 class FrozenError(AttributeError):
     msg: str = ...
 

src/attr/filters.pyi

@@ -2,6 +2,5 @@ from typing import Any, Union
 
 from . import Attribute, _FilterType
 
-
 def include(*what: Union[type, Attribute[Any]]) -> _FilterType[Any]: ...
 def exclude(*what: Union[type, Attribute[Any]]) -> _FilterType[Any]: ...

src/attr/setters.pyi

@@ -2,7 +2,6 @@ from typing import Any, NewType, NoReturn, TypeVar, cast
 
 from . import Attribute, _OnSetAttrType
 
-
 _T = TypeVar("_T")
 
 def frozen(

src/attr/validators.pyi

@@ -17,7 +17,6 @@ from typing import (
 
 from . import _ValidatorType
 
-
 _T = TypeVar("_T")
 _T1 = TypeVar("_T1")
 _T2 = TypeVar("_T2")