public long brokerEpoch(int brokerId) {
        BrokerRegistration brokerRegistration = broker(brokerId);
        if (brokerRegistration == null) {
            return -1L;
        }
        return brokerRegistration.epoch();
    }
@Test
    public void testBrokerEpochForNonExistentBroker() {
        assertEquals(-1L, IMAGE1.brokerEpoch(20));
    }