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