@Override
    public String toString() {
        return "Cluster(id = " + clusterResource.clusterId() + ", nodes = " + this.nodes +
            ", partitions = " + this.partitionsByTopicPartition.values() + ", controller = " + controller + ")";
    }
Get all topics.
@return a set of all topics
clients/src/main/java/org/apache/kafka/common/Cluster.java