code: public function get($sourceName, $currencyCode, \DateTime $date = null, $rateType = RateType::MEDIAN)
      {
          if ($date === null) {
              $date = new \DateTime('now');
          }
  
          if ($this->has($sourceName, $currencyCode, $date, $rateType)) {
              return $this->rates[$this->getRateKey($currencyCode, $date, $rateType, $sourceName)];
          }
  
          throw new ExchangeRateException(sprintf('Could not fetch rate for rate currency code "%s" and rate type "%s" on date "%s".', $currencyCode, $rateType, $date->format('Y-m-d')));
      }
docs: {@inheritdoc}