Returns a new set formed by adding a given object to the receiving set.
Original signature is '- (NSSet *)setByAddingObject:(id)anObject'
Available in Mac OS X v10.5 and later.


- anObject (Id)
- The object to add to the set.

A new set formed by adding anObject to the receiving set.

- Available in Monobjc Bridge: 10.6 (For Mac OS X 10.6 and later), 10.5 (For Mac OS X 10.5 and later)