code: public static <K,V> SortedMap<K,V> asImmutable(SortedMap<K, ? extends V> self) {
          return Collections.unmodifiableSortedMap(self);
      }
docs: A convenience method for creating an immutable sorted map.
  
  @param self a SortedMap
  @return an immutable SortedMap
  @see java.util.Collections#unmodifiableSortedMap(java.util.SortedMap)
  @since 1.0