code: public function delete(array $rates)
      {
          /**
           * @var RateInterface $rate
           */
          foreach ($rates as $rate) {
              unset($this->rates[$this->getRateKey($rate->getCurrencyCode(), $rate->getDate(), $rate->getRateType(), $rate->getSourceName())]);
          }
  
          $this->save(array());
      }
docs: {@inheritdoc}