docs: @BetaApi
    public final Operation deleteRegionInstanceGroupManager(
        ProjectRegionInstanceGroupManagerName instanceGroupManager) {
  
      DeleteRegionInstanceGroupManagerHttpRequest request =
          DeleteRegionInstanceGroupManagerHttpRequest.newBuilder()
              .setInstanceGroupManager(
                  instanceGroupManager == null ? null : instanceGroupManager.toString())
              .build();
      return deleteRegionInstanceGroupManager(request);
    }