class FxRateConfig implements ImmutableBean {

  public Optional<QuoteId> getObservableRateKey(CurrencyPair currencyPair) {
    QuoteId quoteId = observableRates.get(currencyPair.toConventional());
    return Optional.ofNullable(quoteId);
  }

  private  FxRateConfig(
      Map<CurrencyPair, QuoteId> observableRates);

}