in core/src/main/scala/org/apache/spark/eventhubs/client/EventHubsClient.scala [148:154]
private def earliestSeqNoF(partition: PartitionId): Future[SequenceNumber] = {
getRunTimeInfoF(partition).map { r =>
val seqNo =
if (r.getIsEmpty) r.getLastEnqueuedSequenceNumber + 1 else r.getBeginSequenceNumber
if (seqNo == -1L) 0L else seqNo
}
}