✨ Overload @post_load decorator to retain the function type

src/marshmallow_generic/decorators.py

@@ -0,0 +1,41 @@
+from collections.abc import Callable
+from typing import Any, Optional, TypeVar, overload
+from typing_extensions import ParamSpec
+
+from marshmallow.decorators import post_load as _post_load
+
+
+_R = TypeVar("_R")
+_P = ParamSpec("_P")
+
+
+@overload
+def post_load(
+    fn: Callable[_P, _R],
+    pass_many: bool = False,
+    pass_original: bool = False,
+) -> Callable[_P, _R]:
+    ...
+
+
+@overload
+def post_load(
+    fn: None = None,
+    pass_many: bool = False,
+    pass_original: bool = False,
+) -> Callable[[Callable[_P, _R]], Callable[_P, _R]]:
+    ...
+
+
+def post_load(
+    fn: Optional[Callable[..., Any]] = None,
+    pass_many: bool = False,
+    pass_original: bool = False,
+) -> Callable[..., Any]:
+    """
+    Typed overload of the original `marshmallow.post_load` decorator function.
+
+    Generic to ensure that the decorated function retains its type.
+    Runtime behavior is unchanged.
+    """
+    return _post_load(fn, pass_many=pass_many, pass_original=pass_original)