To fix the error, change the first parameter of the `reject_none` method from `cls` to `self`, indicating it's an instance method rather than a class method.

---FILEPATH /Users/someone/Projects/proj01/pyright_self_as_first_argument.py
---FIND
```python
    def reject_none(cls, v):
```
---REPLACE
```python
    def reject_none(self, v):
```
---COMPLETE