docs: public Integer getReplyCode() {
          Object replyCode = getHeader(FtpMessageHeaders.FTP_REPLY_CODE);
  
          if (replyCode != null) {
              if (replyCode instanceof Integer) {
                  return (Integer) replyCode;
              } else {
                  return Integer.valueOf(replyCode.toString());
              }
          } else if (commandResult != null) {
              return Optional.ofNullable(commandResult.getReplyCode()).map(Integer::valueOf).orElse(FTPReply.COMMAND_OK);
          }
  
          return null;
      }