public static long getSequenceId(Cell c) {
    if (c instanceof ExtendedCell) {
      return ((ExtendedCell) c).getSequenceId();
    } else {
      return HConstants.NO_SEQNUM;
    }
  }
Returns ExtendedCellScanner interface over <code>cellIterable</code> or null if
<code>cells</code> is null
hbase-common/src/main/java/org/apache/hadoop/hbase/PrivateCellUtil.java