SET - The sets to create; this does extend SetOf<SET,LINK>, but this cannot
            be stated in Java generics. This means that the results from the methods
            in this interface are immutable.ITEM - The items in such sets.public interface SetFactory<ITEM,SET> extends Factory<SET>
SET copyBackingCollection(Iterable<? extends ITEM> c)
c - The members of the set.SET empty()