code: public function process($baseCurrencyCode, RatesConfigurationRegistryInterface $configurations, array $rates)
      {
          $baseCurrencyCode = CurrencyCodeUtil::clean($baseCurrencyCode);
  
          /**
           * @var RateInterface $rate
           */
          foreach ($rates as $rate) {
  
              if ($baseCurrencyCode !== $rate->getBaseCurrencyCode()) {
                  throw new ConfigurationException(sprintf('Invalid base currency code "%s" of rate "%s" from source "%s" is not calculated.', $rate->getBaseCurrencyCode(), $rate->getCurrencyCode(), $rate->getSourceName()));
              }
          }
  
          return $rates;
      }
docs: {@inheritdoc}