code: protected function loadCurrencyOverride($currency)
      {
          if (is_string($currency) && strlen($currency) === 3) {
              $this->addPriceType(PricingTicketing::PRICETYPE_OVERRIDE_CURRENCY_CONVERSION);
  
              $this->conversionRate = new ConversionRate($currency);
          }
      }
docs: Set currency override code if needed
  
  @param string|null $currency