docs: @BetaApi
    public final ListRegionInstanceGroupManagersPagedResponse listRegionInstanceGroupManagers(
        ProjectRegionName region) {
      ListRegionInstanceGroupManagersHttpRequest request =
          ListRegionInstanceGroupManagersHttpRequest.newBuilder()
              .setRegion(region == null ? null : region.toString())
              .build();
      return listRegionInstanceGroupManagers(request);
    }