auto result = module.walk([&](tf_device::ClusterOp tpu_cluster) {
    std::optional<std::string> host_device;
    if (pass_host_device) {
      std::string host_device_value;
      if (failed(tensorflow::GetHostDeviceOutsideComputation(
              devices, tpu_cluster, &host_device_value)))
        return WalkResult::interrupt();
      host_device = host_device_value;
    }
    cluster_to_host[tpu_cluster.getOperation()] = host_device;