public RichIterable<V> valuesView() {
   return LazyIterate.adapt(this.values());
 }
 public RichIterable<Pair<K, V>> keyValuesView() {
   return LazyIterate.adapt(this.entrySet())
       .collect(AbstractImmutableEntry.<K, V>getPairFunction());
 }
 public RichIterable<K> keysView() {
   return LazyIterate.adapt(this.keySet());
 }