example.py

import functools
import inspect


def check_spec(func: callable, kwargs: dict):
    spec = inspect.getfullargspec(func)
    if spec.varkw:
        return kwargs

    return {k: v for k, v in kwargs.items() if k in spec.args}


def safe_kwargs(func_or_class):
    @functools.wraps(func_or_class)
    def wrap(*args, **kwargs):
        spec = check_spec(func_or_class, kwargs)
        return func_or_class(*args, **spec)

    return wrap


@safe_kwargs
class Foo:
    def __init__(self, foo, bar=None):
        print(foo, bar)


Foo(42, bar='asdsad', baz='asdasd')