code: public static <T> Set<T> asUnmodifiable(Set<T> self) {
          return Collections.unmodifiableSet(self);
      }
docs: Creates an unmodifiable view of a Set.
  
  @param self a Set
  @return an unmodifiable view of the Set
  @see java.util.Collections#unmodifiableSet(java.util.Set)
  @see #asUnmodifiable(java.util.List)
  @since 2.5.0