@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        TopicMetadata that = (TopicMetadata) o;

        if (!id.equals(that.id)) return false;
        if (!name.equals(that.name)) return false;
        if (numPartitions != that.numPartitions) return false;
        return partitionRacks.equals(that.partitionRacks);
    }
@return Every partition mapped to the set of corresponding available rack Ids of its replicas.
        An empty map is returned if rack information is unavailable for all partitions.
group-coordinator/src/main/java/org/apache/kafka/coordinator/group/modern/TopicMetadata.java