Improve hints in migration Operation class (#996)

django-stubs/db/migrations/operations/base.pyi

@@ -1,18 +1,27 @@
-from typing import Any, Dict, List, Sequence, Tuple, Union
+from typing import Any, Dict, List, Sequence, Tuple, Type, Union
+
+from django.db.backends.base.base import BaseDatabaseWrapper
+from django.db.backends.base.schema import BaseDatabaseSchemaEditor
+from django.db.migrations.state import ProjectState
+from django.db.models import Model
 
 class Operation:
     reversible: bool = ...
     reduces_to_sql: bool = ...
     atomic: bool = ...
     elidable: bool = ...
-    serialization_expand_args: Any = ...
+    serialization_expand_args: List[str] = ...
     _constructor_args: Tuple[Sequence[Any], Dict[str, Any]]
     def deconstruct(self) -> Tuple[str, Sequence[Any], Dict[str, Any]]: ...
-    def state_forwards(self, app_label: Any, state: Any) -> None: ...
-    def database_forwards(self, app_label: Any, schema_editor: Any, from_state: Any, to_state: Any) -> None: ...
-    def database_backwards(self, app_label: Any, schema_editor: Any, from_state: Any, to_state: Any) -> None: ...
+    def state_forwards(self, app_label: str, state: ProjectState) -> None: ...
+    def database_forwards(
+        self, app_label: str, schema_editor: BaseDatabaseSchemaEditor, from_state: ProjectState, to_state: ProjectState
+    ) -> None: ...
+    def database_backwards(
+        self, app_label: str, schema_editor: BaseDatabaseSchemaEditor, from_state: ProjectState, to_state: ProjectState
+    ) -> None: ...
     def describe(self) -> str: ...
     def references_model(self, name: str, app_label: str) -> bool: ...
     def references_field(self, model_name: str, name: str, app_label: str) -> bool: ...
-    def allow_migrate_model(self, connection_alias: Any, model: Any) -> bool: ...
+    def allow_migrate_model(self, connection_alias: Union[BaseDatabaseWrapper, str], model: Type[Model]) -> bool: ...
     def reduce(self, operation: Operation, app_label: str) -> Union[bool, List[Operation]]: ...