docs: private void extractSequenceCount() {
          if (this.sequenceCount == -1) {
              final int seqCnt = payload.getUnsignedByte(HEADER_PART_SEQCNT_START);
              if (seqCnt >= 0) {
                  this.sequenceCount = seqCnt;
              } else {
                  throw new IllegalStateException("Could not extract sequence count");
              }
          }
      }