Argument of type "None" cannot be assigned to parameter "stop_words" of type "str | List[str]" in function "extract_keywords"

Small warning between the documentation and the code implementation (nothing serious)

With the bellow code I have a warning:
Argument of type "None" cannot be assigned to parameter "stop_words" of type "str | List[str]" in function "extract_keywords"
Type "None" is not assignable to type "str | List[str]"
"None" is not assignable to "str"
"None" is not assignable to "List[str]"
```python
sim = kw_model.extract_keywords(text,
keyphrase_ngram_range=(1, 1),
stop_words=None,
vectorizer=vectorizer,
top_n=list_words.__len__())
```

I'm not sure this is intended, as in the following example in the documentation, stop_words is None.
```python
>>> kw_model.extract_keywords(doc, keyphrase_ngram_range=(1, 1), stop_words=None)
[('learning', 0.4604),
('algorithm', 0.4556),
('training', 0.4487),
('class', 0.4086),
('mapping', 0.3700)]
```

So should the documentation or code be changed?

Start at the extract_keywords entry point and compare the stop_words type accepted by the implementation with the documentation example that passes None. Check the relevant typing or documentation source, then update the inconsistent part and verify that the warning and example agree.

Written by the indexing model from the issue text.