code: public String getServiceUrlGroup(String version, String service) {
      String[] groups = config.getStringArray("api.adwords.version." + version + ".groups");
      for (String group : groups) {
        String[] services =
            config.getStringArray("api.adwords.version." + version + "." + group + ".services");
        if (Lists.newArrayList(services).contains(service)) {
          return group;
        }
      }
      throw new NullPointerException("No group found for service: " + version + "." + service);
    }
docs: Gets the service URL group for the service and version.