Fix stubs and add tests

src/dependency_injector/containers.pyi

@@ -1,5 +1,5 @@
 from types import ModuleType
-from typing import Type, Dict, Tuple, Optional, Any, Union, ClassVar, Callable as _Callable, Iterable
+from typing import Type, Dict, Tuple, Optional, Any, Union, ClassVar, Callable as _Callable, Iterable, TypeVar
 
 from .providers import Provider
 
@@ -31,9 +31,12 @@ class DeclarativeContainer(Container):
     def __init__(self, **overriding_providers: Union[Provider, Any]) -> None: ...
 
 
-def override(container: Container) -> _Callable[[Container], Container]: ...
+C = TypeVar('C', bound=DeclarativeContainer)
 
 
-def copy(container: Container) -> _Callable[[Container], Container]: ...
+def override(container: Type[C]) -> _Callable[[Type[C]], Type[C]]: ...
+
+
+def copy(container: Type[C]) -> _Callable[[Type[C]], Type[C]]: ...
 
 def is_container(instance: Any) -> bool: ...

tests/typing/declarative_container.py

@@ -10,3 +10,23 @@ container1 = Container1()
 container1_type: containers.Container = Container1()
 provider1: providers.Provider = container1.provider
 val1: int = container1.provider(3)
+
+
+# Test 2: to check @override decorator
+class Container21(containers.DeclarativeContainer):
+    provider = providers.Factory(int)
+
+
+@containers.override(Container21)
+class Container22(containers.DeclarativeContainer):
+    ...
+
+
+# Test 3: to check @copy decorator
+class Container21(containers.DeclarativeContainer):
+    provider = providers.Factory(int)
+
+
+@containers.copy(Container21)
+class Container22(containers.DeclarativeContainer):
+    ...