private static void addDefaultFields(SortedSet<PdxField> myFields,
      SortedSet<PdxField> otherFields) {
    for (PdxField f : otherFields) {
      if (!myFields.contains(f)) {
        myFields.add(new DefaultPdxField(f));
      }
    }
  }
Any fields that are in otherFields but not in myFields are added to myFields as defaults. When
adding fields they are inserted in the natural sort order. Note: myFields may be modified by
this call.
geode-core/src/main/java/org/apache/geode/pdx/internal/PdxInstanceImpl.java