code: public boolean isSet(_Fields field) {
      if (field == null) {
        throw new IllegalArgumentException();
      }
  
      switch (field) {
      case STATUS:
        return isSetStatus();
      case OPERATION_STATE:
        return isSetOperationState();
      case SQL_STATE:
        return isSetSqlState();
      case ERROR_CODE:
        return isSetErrorCode();
      case ERROR_MESSAGE:
        return isSetErrorMessage();
      }
      throw new IllegalStateException();
    }
docs: Returns true if field corresponding to fieldID is set (has been assigned a value) and false otherwise