private Predicate<Attribute> hostAttrFilter() {
        return attribute -> attribute.getName().equalsIgnoreCase("pod")
            || attribute.getName().equalsIgnoreCase("hostname");
    }
@return return the related service hierarchy recursively, e.g. A-B-C, query A will return A-B, B-C
If the relation could be conjectured will be removed, e.g. A-B-C-D and A-D, query A will return A-B, B-C, C-D because A-D could be conjectured.
oap-server/server-core/src/main/java/org/apache/skywalking/oap/server/core/query/HierarchyQueryService.java