GetItemResult
class GetItemResult(val item: DhtItem?, val closestWithTokens: List<Pair<CompactNode, ByteArray>>, val observedSeq: Long?)
Result of getItem: the best item found (or null), the closest token-bearing nodes, and observedSeq, the highest mutable sequence number seen across responders. Use that as the cas value for a following mutable putItem. It is null if nothing was found.