Set<Uuid> topicsAwaitingReconciliation() {
        return topicPartitionsAwaitingReconciliation().keySet();
    }
@return Set of topic IDs received in a target assignment that have not been reconciled yet
because topic names are not in metadata or reconciliation hasn't finished. Reconciliation
hasn't finished for a topic if the currently active assignment has a different set of partitions
for the topic than the target assignment.

Visible for testing.
clients/src/main/java/org/apache/kafka/clients/consumer/internals/MembershipManagerImpl.java