code: public static <K, V> SortedSetMultimap<K, V> constrainedSortedSetMultimap(
        SortedSetMultimap<K, V> multimap,
        MapConstraint<? super K, ? super V> constraint) {
      return new ConstrainedSortedSetMultimap<K, V>(multimap, constraint);
    }
docs: Returns a constrained view of the specified sorted-set multimap, using the
  specified constraint. Any operations that add new mappings will call the
  provided constraint. However, this method does not verify that existing
  mappings satisfy the constraint.
  
  <p>Note that the generated multimap's {@link Multimap#removeAll} and
  {@link Multimap#replaceValues} methods return collections that are not
  constrained.
  <p>The returned multimap is not serializable.
  
  @param multimap the multimap to constrain
  @param constraint the constraint that validates added entries
  @return a constrained view of the specified multimap