docs: @BetaApi
    public final Operation deleteInstancesRegionInstanceGroupManager(
        ProjectRegionInstanceGroupManagerName instanceGroupManager,
        RegionInstanceGroupManagersDeleteInstancesRequest
            regionInstanceGroupManagersDeleteInstancesRequestResource) {
  
      DeleteInstancesRegionInstanceGroupManagerHttpRequest request =
          DeleteInstancesRegionInstanceGroupManagerHttpRequest.newBuilder()
              .setInstanceGroupManager(
                  instanceGroupManager == null ? null : instanceGroupManager.toString())
              .setRegionInstanceGroupManagersDeleteInstancesRequestResource(
                  regionInstanceGroupManagersDeleteInstancesRequestResource)
              .build();
      return deleteInstancesRegionInstanceGroupManager(request);
    }