code: protected void doNotifyListenersOfRemovedValues(Map<K, R> oldValues) {
          List<MapValueChangeListener<K, R>> listenersCopy = new ArrayList<MapValueChangeListener<K, R>>(listeners);
          Map<K, R> unmodifiable = Collections.unmodifiableMap(oldValues);
          for (MapValueChangeListener<K, R> listener : listenersCopy) {
              listener.valuesRemoved(this, unmodifiable);
          }
      }
docs: Notifies the change listeners that values have been removed.
  <p>
  Note that the specified map of values will be wrapped in an unmodifiable map before being passed to the
  listeners.
  
  @param oldValues Removed values.