code: public boolean isSet(_Fields field) {
      if (field == null) {
        throw new IllegalArgumentException();
      }
  
      switch (field) {
      case TRANSACTION_ID:
        return isSetTransactionId();
      case READ_POINTER:
        return isSetReadPointer();
      case INVALIDS:
        return isSetInvalids();
      case IN_PROGRESS:
        return isSetInProgress();
      case FIRST_SHORT:
        return isSetFirstShort();
      case TYPE:
        return isSetType();
      case WRITE_POINTER:
        return isSetWritePointer();
      case CHECKPOINT_WRITE_POINTERS:
        return isSetCheckpointWritePointers();
      case VISIBILITY_LEVEL:
        return isSetVisibilityLevel();
      }
      throw new IllegalStateException();
    }
docs: Returns true if field corresponding to fieldID is set (has been assigned a value) and false otherwise