docs: @BetaApi
    public final InstanceGroupManager getRegionInstanceGroupManager(
        ProjectRegionInstanceGroupManagerName instanceGroupManager) {
  
      GetRegionInstanceGroupManagerHttpRequest request =
          GetRegionInstanceGroupManagerHttpRequest.newBuilder()
              .setInstanceGroupManager(
                  instanceGroupManager == null ? null : instanceGroupManager.toString())
              .build();
      return getRegionInstanceGroupManager(request);
    }