Adds exception when no device is found

src/models/exceptions.py

@@ -0,0 +1,2 @@
+class NoDeviceFoundError(Exception):
+    pass

src/models/helper.py

@@ -1,5 +1,6 @@
 from typing import TypeVar
 from models.devices import GenericDevice, LightDevice, SwitchDevice
+from models.exceptions import NoDeviceFoundError
 from models.groups import DeviceGroup, Room
 
 
@@ -8,4 +9,9 @@ DEVICE_TYPE = TypeVar("DEVICE_TYPE", type(GenericDevice), type(SwitchDevice), ty
 
 def filter_devices(devices: list[GenericDevice], type: DEVICE_TYPE) -> list[DEVICE_TYPE]:
     """Filters out devices that are not of a specific type."""
-    return [device for device in devices if isinstance(device, DEVICE_TYPE)]
+    filtered_devices: list[type] = [device for device in devices if isinstance(device, type)]
+    
+    if len(filtered_devices) == 0:
+        raise NoDeviceFoundError(f"No devices of type {type} found.")
+    
+    return filtered_devices