docs: @BetaApi
    public final ListRegionInstanceGroupsPagedResponse listRegionInstanceGroups(
        ProjectRegionName region) {
      ListRegionInstanceGroupsHttpRequest request =
          ListRegionInstanceGroupsHttpRequest.newBuilder()
              .setRegion(region == null ? null : region.toString())
              .build();
      return listRegionInstanceGroups(request);
    }