// function and deleted (as the backprop code creates lots of gradients the user
// is not interested in).
//
// BackwardFunction needs to be a closure which stores intermediate activations
// from the forward computation and calls a vector-jacobian product function
// (also known as adjoint function) to compute, given downstream gradients,
// upstream gradients.
//

  // partitioned tensor are combined into a single entry.
  const TensorSliceReader::VarToDataTypeMap& GetVariableToDataTypeMap() const;

  // Attempts to look up the tensor named "name" and stores the found result in
  // "out_tensor".
  void GetTensor(const string& name,
                 std::unique_ptr<tensorflow::Tensor>* out_tensor,
                 TF_Status* out_status) const;

 private:

                                                    TF_Status* status);

// Get task states from the Coordination Service.
TF_CAPI_EXPORT extern void TFE_GetTaskStates(TFE_Context* ctx,
                                             const TF_Buffer& tasks,
                                             void* states, TF_Status* status);

TF_CAPI_EXPORT extern void TFE_WaitAtBarrier(TFE_Context* ctx,

                                              size_t proto_len,
                                              TF_Status* status);

// Starts an in-process TensorFlow server.
TF_CAPI_EXPORT extern void TF_ServerStart(TF_Server* server, TF_Status* status);

// Stops an in-process TensorFlow server.
TF_CAPI_EXPORT extern void TF_ServerStop(TF_Server* server, TF_Status* status);