public Map<TopicPartition, KafkaFuture<Void>> values() {
        return futures;
    }
Return a map from partitions to futures which can be used to check the status of the reassignment.

Possible error codes:

INVALID_REPLICA_ASSIGNMENT (39) -  if the specified replica assignment was not valid -- for example, if it included negative numbers, repeated numbers, or specified a broker ID that the controller was not aware of.
NO_REASSIGNMENT_IN_PROGRESS (85) - if the request wants to cancel reassignments but none exist
UNKNOWN (-1)
clients/src/main/java/org/apache/kafka/clients/admin/AlterPartitionReassignmentsResult.java