code: public void append(long startDrId, long endDrId, long spUniqueId, long mpUniqueId) {
          assert(startDrId <= endDrId && (m_map.isEmpty() || startDrId > end(m_map.span())));
  
          addRange(startDrId, endDrId, spUniqueId, mpUniqueId);
      }
docs: Appends a range to the tracker. The range has to be after the last DrId
  of the tracker.
  @param startDrId
  @param endDrId
  @param spUniqueId
  @param mpUniqueId