@Override
    public void toData(PdxWriter writer) {
      ((PdxWriterImpl) writer).setDoExtraValidation(true);
      writer.writeInt("fieldCount", fieldCount);
      for (int i = 0; i < fieldCount; i++) {
        writer.writeField("f" + i, null, fieldType);
      }
    }
Init fields using base as appropriate, but does not initialize aQueryObject field.

@param base The base value for all fields. Fields are all set to a value using base as
       appropriate.
@param useNulls If true, fill in nulls for those fields that can be set to null (to test null
       values), if false, then use a valid value (to test non-null values).
geode-core/src/integrationTest/java/org/apache/geode/pdx/PdxSerializableJUnitTest.java