void PopState() { call_state_.pop(); }

 private:
  // Helper for Accumulate: uses a GradientTape to compute forward gradients
  // from a backward gradient function. Fills `out_grads` corresponding to
  // `output_tensors`. `out_grads` must not be null.
  //
  // Executes the backward function in order to trace its gradient, which will

// Get a set of node names that must be preserved. They can not be transformed
// or removed during the graph transformation. This includes feed and fetch
// nodes, keep_ops, init_ops. Fills in `num_values` and `storage_size`, they
// will be used in `TF_GetNodesToPreserveList`.
TF_CAPI_EXPORT extern void TF_GetNodesToPreserveListSize(
    const TF_GrapplerItem* item, int* num_values, size_t* storage_size,