// 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:

// `GradientTape::Watch`.) The op_id is simply a unique index assigned to each
// op executed under the tape. A separate map (`tensorflow::eager::OpTape`)
// maintains the map from `op_id` to a `OpTapeEntry` which stores the `op_type`,
// inputs and outputs and the gradient function These data structures combined
// allow us to trace the data dependencies between operations and hence compute
// gradients.
//

                                                    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);

TF_CAPI_EXPORT extern const char* TFE_TensorHandleBackingDeviceName(
    TFE_TensorHandle* h, TF_Status* status);

// Return a pointer to a new TFE_TensorHandle that shares the underlying tensor
// with `h`. On success, `status` is set to OK. On failure, `status` reflects
// the error and a nullptr is returned.
TF_CAPI_EXPORT extern TFE_TensorHandle* TFE_TensorHandleCopySharingTensor(