// is for performance optimization by reusing an exiting unused op rather than
// creating a new op every time. If `raw_device_name` is `NULL` or empty, it
// does not set the device name. If it's not `NULL`, then it attempts to parse
// and set the device name. It's effectively `TFE_OpSetDevice`, but it is faster
// than separately calling it because if the existing op has the same

} TF_TriState;

// TF_GrapplerItem represents a combination of a graph, one of more fetch nodes,
// and potentially a set of nodes to feed.
typedef struct TF_GrapplerItem TF_GrapplerItem;

// Flags indicating whether existing optimizers should be turned off.
// It's optional for plugin to set functions to return true/false. If not
// set, proper uses configuration set by user.
typedef struct TP_OptimizerConfigs {
  size_t struct_size;

  typename std::unordered_map<int64_t, Gradient*>::iterator existing =
      accumulated_gradients_.find(tensor_id);
  vspace_.MarkAsResult(tangent);
  if (existing == accumulated_gradients_.end()) {
    accumulated_gradients_.emplace(tensor_id, tangent);
  } else {
    std::array<Gradient*, 2> to_aggregate;
    to_aggregate[0] = tangent;
    to_aggregate[1] = existing->second;

               char* buffer, TF_Status* status);

  // Validate the given file signature with the existing file signature in the
  // cache. Returns true if the signature doesn't change or the file doesn't
  // exist before. If the signature changes, update the existing signature with
  // the new one and remove the file from cache.
  bool ValidateAndUpdateFileSignature(const std::string& filename,