code: public static <T> Set<T> dup(Collection<T> collection)
  	{
  		if(isEmpty(collection))
  			return new HashSet<T>();
  		return new HashSet<T>(collection);
  	}
docs: Duplicate set.
  This allow's the default Set implementation to be swapped
  easily.
  @param set The set to dupplicate.
  @return a new empty set.