You can use the [`classmethod`](https://docs.python.org/3/library/functions.html#classmethod) decorator, which is more appropriate for this situation anyways:

```python
class C:
 class Nested:
 counter = 0

 @classmethod
 def increment(cls) -> int:
 cls.counter += 1
 return cls.counter

print(C().Nested.increment()) # prints 1
```

If you are wondering why `increment` can't find `Cl_static_parameter_nested` in your example: you would have to write `Cl_some_class.Cl_static_parameter_nested` to access it from the global namespace.