If you don't want a part to be written out, you can override the setDefaultOnNonWritingFields() method to call the base class version first. Then, for any part you don't want written out, call
partName.setDefault(TRUE);
Be aware, though, that the part may write out anyway under certain conditions. For example, if the part lies on a path that is being written to a file, the part will write out regardless of this setting.