code: public static final <T> Set<T> symmetricDifference(Set<T>... sets)
      {
          return symmetricDifference(CollectionHelp.create(sets));
      }
docs: Symmetric difference of sets A and B, denoted A △ B or A ⊖ B,
  is the set of all objects that are a member of exactly one of A and B
  (elements which are in one of the sets, but not in both)
  @param <T>
  @param sets
  @return