@Override
  public boolean isValidMessageCode(final int protocolVersion, final int code) {
    switch (code) {
      case QbftV1.PROPOSAL:
      case QbftV1.PREPARE:
      case QbftV1.COMMIT:
      case QbftV1.ROUND_CHANGE:
        return true;

      default:
        return false;
    }
  }
Get istanbul100 sub protocol.

@return the istanbul100 sub protocol
consensus/qbft/src/main/java/org/hyperledger/besu/consensus/qbft/protocol/Istanbul100SubProtocol.java