public SampleFamily instance(List<String> serviceKeys, List<String> instanceKeys, Layer layer) {
        return instance(serviceKeys, Const.POINT, instanceKeys, Const.POINT, layer, null);
    }
Following operations are used in DSL
oap-server/analyzer/meter-analyzer/src/main/java/org/apache/skywalking/oap/meter/analyzer/dsl/SampleFamily.java