magic_reset: Add warning about __slots__

Also add __slots__ to will_reset_to.

Author: auscompgeek

magicbot/magic_reset.py

@@ -22,7 +22,11 @@ def execute(self):
         
         
         .. note:: This will only work for MagicRobot components
+
+        .. warning:: This will not work on classes that set ``__slots__``.
     """
 
+    __slots__ = ("default",)
+
     def __init__(self, default):
         self.default = default