docs: public void setWindowMillis(long windowMillis) {
          FailureInterpreter fi = getFailureInterpreter();
          if (!(fi instanceof DefaultFailureInterpreter)) {
              throw new IllegalStateException("setWindowMillis() not supported: this CircuitBreaker's FailureInterpreter isn't a DefaultFailureInterpreter.");
          }
          ((DefaultFailureInterpreter)fi).setWindowMillis(windowMillis);
      }