Add input-check as suggested

Author: bouwew

plugwise/__init__.py

@@ -406,6 +406,9 @@ async def set_switch_state(
           - False when switched to state off,
           - the unchanged state when the switch is for instance locked.
         """
+        if state not in (STATE_ON, STATE_OFF):
+            raise PlugwiseError("Invalid state supplied to set_switch_state")
+
         try:
             return await self._smile_api.set_switch_state(
                 appl_id, members, model, state

plugwise/constants.py

@@ -23,6 +23,7 @@
 PRESET_AWAY: Final = "away"
 PRESSURE_BAR: Final = "bar"
 SIGNAL_STRENGTH_DECIBELS_MILLIWATT: Final = "dBm"
+STATE_OFF: Final = "off"
 STATE_ON: Final = "on"
 TEMP_CELSIUS: Final = "°C"
 TEMP_KELVIN: Final = "°K"