Enhance ModelView class with iterable and indexing support

- Added iterator, length, and item access methods to the `ModelView` class, allowing it to handle single models and lists more effectively.
- Refactored the `vlans` method in the `Keenetic` model to restore functionality for decoding VLAN descriptions, improving data processing consistency.

oxi/interfaces/models/keenetic.py

@@ -33,13 +33,13 @@ class Keenetic(BaseDevice):
                 item["description"] = decoded
         return interfaces
 
-    # def vlans(self):
-    #     vlans = self.raw["vlans"]
-    #     for item in vlans:
-    #         if item.get("description"):
-    #             decoded = self._decode_utf(item.get("description", ""))
-    #             item["description"] = decoded
-    #     return vlans
+    def vlans(self):
+        vlans = self.raw["vlans"]
+        for item in vlans:
+            if item.get("description"):
+                decoded = self._decode_utf(item.get("description", ""))
+                item["description"] = decoded
+        return vlans
 
 
 if __name__ == "__main__":