void TF_AddOperationControlInput(TF_Graph* graph, TF_Operation* op,
                                 TF_Operation* input) {
  using tensorflow::RecordMutation;
  mutex_lock l(graph->mu);
  graph->graph.AddControlEdge(&input->node, &op->node);
  RecordMutation(graph, *op, "adding control input");
}

void TF_SetAttr(TF_Graph* graph, TF_Operation* op, const char* attr_name,