human
I wrote the below code

    assert (num_threads > 0)
    has_kwargs_list = (kwargs_list is not None)
    if has_kwargs_list:
        assert (len(kwargs_list) == num_threads)
    import threading
    def wrapper(func):
        @wraps(func)
        def inner(*args, **kwargs):
            if has_kwargs_list:
                update_kwargs = (lambda i: dict(kwargs, **kwargs_list[i]))
            else:
                update_kwargs = (lambda i: kwargs)
            threads = []
            for i in range(num_threads):
                updated_kwargs = update_kwargs(i)
                thread = threading.Thread(target=func, args=args, kwargs=updated_kwargs)
                threads.append(thread)
            for thread in threads:
                thread.start()
            for thread in threads:
                thread.join()
        return inner
    return wrapper

What's a good function header?
 Here's a good function header?
assistant
#Here's a good function header.

def test_parallel(num_threads=2, kwargs_list=None):