@Override
                protected boolean retainTopic(String topic, boolean isInternal, long nowMs) {
                    return retainTopics.get().contains(topic);
                }
Prior to Kafka version 2.4 (which coincides with Metadata version 9), the broker does not propagate leader epoch
information accurately while a reassignment is in progress, so we cannot rely on it. This is explained in more
detail in MetadataResponse's constructor.
clients/src/test/java/org/apache/kafka/clients/MetadataTest.java