//           can be null. The names used for function inputs are normalized
//           names of the operations (usually placeholders) pointed to by
//           `inputs`. These operation names should start with a letter.
//           Normalization will convert all letters to lowercase and
//           non-alphanumeric characters to '_' to make resulting names match
//           the "[a-z][a-z0-9_]*" pattern for operation argument names.

  std::atomic<bool> extend_before_run;
};

struct TF_ImportGraphDefOptions {
  tensorflow::ImportGraphDefOptions opts;

  // Backing memory for TensorId fields in opts.
  // TODO(skyewm): it'd be better if ImportGraphDefOptions owned this.
  std::vector<tensorflow::string> tensor_id_data;
};

struct TF_ImportGraphDefResults {
  std::vector<TF_Output> return_tensors;
  std::vector<TF_Operation*> return_nodes;

      absl::Span<const int64_t> input_tensor_id,
      absl::Span<const tensorflow::DataType> input_dtypes,
      const std::function<BackwardFunction*()>& backward_function_getter,
      const std::function<void(BackwardFunction*)>& backward_function_deleter);

  void DeleteTrace(int64_t tensor_id);

  // Consumes the internal state of the tape (so cannot be called more than