code: public void multiKeyBackupAck(long id, Address from, int segment, int topologyId) {
        SegmentBasedCollector collector = (SegmentBasedCollector) collectorMap.get(id);
        if (collector != null) {
           collector.backupAck(from, segment, topologyId);
        }
     }
docs: Acknowledges a {@link org.infinispan.commands.write.PutMapCommand} completion in the backup owner.
  
  @param id         the id from {@link CommandInvocationId#getId()}.
  @param from       the backup owner.
  @param segment    the segments affected and acknowledged.
  @param topologyId the topology id.