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