mutex_lock l(mu_);
  return status_;
}

Status QueueRunner::ExportCostGraph(CostGraphDef* cost_graph) const {
  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();
}

  mutex_lock l(mu_);
  while (!should_stop_) {
    wait_for_stop_.wait(l);
  }
}

Status Coordinator::ExportCostGraph(CostGraphDef* cost_graph) const {
  mutex_lock l(runners_lock_);
  for (auto& t : runners_) {
    Status s = t->ExportCostGraph(cost_graph);
    if (!s.ok()) {
      return s;
    }
  }
  return absl::OkStatus();
}

  *input = {oper, 0};
  return true;
}

// Copies `src_graph` into `dst_graph`. Any node in `src_graph` with input
// `src_inputs[i]` will have that input replaced with `dst_inputs[i]`.  `prefix`
// will be prepended to copied node names. `control_deps` are nodes in
// `dst_graph` that the copied `src_graph` nodes will have control dependencies