@Override
    public String topicSource(String topic) {
        if (looksLikeHeartbeat(topic)) {
            return super.topicSource(topic);
        } else {
            return sourceClusterAlias;
        }
    }
Unlike {@link DefaultReplicationPolicy}, IdentityReplicationPolicy cannot know the source of
a remote topic based on its name alone. If <code>source.cluster.alias</code> is provided,
this method will return that.
<p>
In the special case of heartbeats, we defer to {@link DefaultReplicationPolicy#topicSource(String)}.
connect/mirror-client/src/main/java/org/apache/kafka/connect/mirror/IdentityReplicationPolicy.java