chore: add a class comment about availability

Author: allenporter

roborock/devices/traits/v1/consumeable.py

@@ -34,7 +34,11 @@ def from_str(cls, value: str) -> Self:
 
 
 class ConsumableTrait(Consumable, common.V1TraitMixin):
-    """Trait for managing consumable attributes on Roborock devices."""
+    """Trait for managing consumable attributes on Roborock devices.
+    
+    After the first refresh, you can tell what consumables are supported by
+    checking which attributes are not None.
+    """
 
     command = RoborockCommand.GET_CONSUMABLE