FieldSet parseSpecialValues(String name)
    {
        if (name.equals(DocIdOnly.NAME)) { return new DocIdOnly(); }
        else if (name.equals(DocumentOnly.NAME)) { return (new DocumentOnly()); }
        else if (name.equals(AllFields.NAME)) { return (new AllFields()); }
        else if (name.equals(NoFields.NAME)) { return (new NoFields()); }
        else if (name.equals("[docid]")) { return (new DocIdOnly()); }
        else {
            throw new IllegalArgumentException(
                    "The only special names (enclosed in '[]') allowed are " +
                    "id, all, document, none");
        }
    }
TODO: Move to document and implement
document/src/main/java/com/yahoo/document/fieldset/FieldSetRepo.java