LOG(WARNING) << mutation_warning;
      session->graph->sessions[session].clear();
    }

    const auto num_nodes = graph.num_node_ids();
    if (session->last_num_graph_nodes < num_nodes) {
      // TODO(nolivia): check this on a subset of the graph instead of all of
      // it.
      status->status = graph::ValidateGraphHasNoCycle(session->graph->graph);
      if (!status->status.ok()) {
        session->graph->mu.unlock();