@Override
  public String toUrlValue() {
    if (this == UNKNOWN) {
      throw new UnsupportedOperationException("Shouldn't use PriceLevel.UNKNOWN in a request.");
    }
    return priceLevel;
  }
Indicates an unknown price level type returned by the server. The Java Client for Google Maps
Services should be updated to support the new value.
src/main/java/com/google/maps/model/PriceLevel.java