## Description

This PR fixes an `UnboundLocalError` in the `RepNCSPELAN4` class that occurs when `csp_type` parameter is set to any value other than `'csp2'`.

## Problem

The current implementation in `hybrid_encoder.py` has a conditional assignment issue:

```python
if csp_type == 'csp2':
    CSPLayer = CSPLayer2
self.cv2 = nn.Sequential(CSPLayer(...), ...)  # CSPLayer used here
```

When `csp_type != 'csp2'`, the local variable `CSPLayer` is never assigned, but Python still treats it as a local variable due to the assignment in the `if` block. This prevents falling back to the global `CSPLayer` class and raises: