public static Field p(String fieldName) {
        return SELECT_ALL_FROM_SOURCES_ALL.where(fieldName);
    }
@Test
    void set_group_syntax_string_directly() {
        /*
        example from vespa document:
        https://docs.vespa.ai/en/grouping.html
        all( group(a) max(5) each(output(count())
            all(max(1) each(output(summary())))
            all(group(b) each(output(count())
                all(max(1) each(output(summary())))
                all(group(c) each(output(count())
                    all(max(1) each(output(summary())))))))) );
         */
        String q = Q.p("f1").contains("v1")
                .group("all(group(a) max(5) each(output(count()) all(max(1) each(output(summary()))) all(group(b) each(output(count()) all(max(1) each(output(summary()))) all(group(c) each(output(count()) all(max(1) each(output(summary())))))))))")
                .build();

        assertEquals(q, "yql=select * from sources * where f1 contains \"v1\" | all(group(a) max(5) each(output(count()) all(max(1) each(output(summary()))) all(group(b) each(output(count()) all(max(1) each(output(summary()))) all(group(c) each(output(count()) all(max(1) each(output(summary())))))))))");
    }