```common lisp
(defpackage #:hello-world
  (:use #:cl)
  (:export #:hello))
(in-package #:hello-world)

(defun hello NIL)
```

Replace `NIL` with `()` in stub function definition.
user
```common lisp
(defpackage #:hello-world
  (:use #:cl)
  (:export #:hello))
(in-package #:hello-world)

(defun hello ())
```
assistant