code: public static <K, V> BiMap<K, V> constrainedBiMap(
        BiMap<K, V> map, MapConstraint<? super K, ? super V> constraint) {
      return new ConstrainedBiMap<K, V>(map, null, constraint);
    }
docs: Returns a constrained view of the specified bimap, using the specified
  constraint. Any operations that modify the bimap will have the associated
  keys and values verified with the constraint.
  
  <p>The returned bimap is not serializable.
  
  @param map the bimap to constrain
  @param constraint the constraint that validates added entries
  @return a constrained view of the specified bimap