Add stubs for providers module functions

src/dependency_injector/providers.pyi

@@ -135,3 +135,21 @@ class ItemGetter(Provider, ProvidedInstanceFluentInterface):
 
 class MethodCaller(Provider, ProvidedInstanceFluentInterface):
     def __init__(self, provider: Provider, *args: Injection, **kwargs: Injection) -> None: ...
+
+
+def is_provider(instance: Any) -> bool: ...
+
+
+def ensure_is_provider(instance: Any) -> Provider: ...
+
+
+def is_delegated(instance: Any) -> bool: ...
+
+
+def represent_provider(provider: Provider, provides: Any) -> str: ...
+
+
+def deepcopy(instance: Any, memo: Optional[Dict[str, Any]]): Any: ...
+
+
+def merge_dicts(dict1: Dict[Any, Any], dict2: Dict[Any, Any]) -> Dict[Any, Any]: ...