code: public static <T> Set<T> asImmutable(Set<? extends T> self) {
          return Collections.unmodifiableSet(self);
      }
docs: A convenience method for creating an immutable list.
  
  @param self a Set
  @return an immutable Set
  @see java.util.Collections#unmodifiableSet(java.util.Set)
  @since 1.0