if (!cg_mu_) {
    return Status(absl::StatusCode::kFailedPrecondition,
                  "This QueueRunner doesn't collect a cost graph.");
  }
  mutex_lock l(*cg_mu_);
  cost_graph->MergeFrom(*cost_graph_);
  return absl::OkStatus();
}

void QueueRunner::SetRunArgumentsAndCostGraph(const RunOptions& run_options) {
  cg_mu_.reset(new mutex());
  {
    mutex_lock l(*cg_mu_);