Stores NewValue in the slot specified by SlotName.
This predicate may only appear in the body of a method clause, and it always operates on the object to which that message is sent. It cannot be used to directly modify the slots of another object.
either argument is unbound.
NewValue is not of the appropriate type for Slotname.
Slotname is not the name of a slot of the current class.
Slotname is a private slot of a superclass.