TFE_CancellationManager*);
TF_CAPI_EXPORT extern bool TFE_CancellationManagerRegisterCallback(
    TFE_CancellationManager*, TFE_CancellationToken token,
    const TFE_CancelCallback* c_callback, const char* callback_name);
TF_CAPI_EXPORT extern bool TFE_CancellationManagerDeregisterCallback(
    TFE_CancellationManager*, TFE_CancellationToken token);
TF_CAPI_EXPORT extern bool TFE_CancellationManagerTryDeregisterCallback(

  virtual void ClearCachesAndThreadExecutors() = 0;

  // Initialize the step resource container for a training step. This is used
  // in current TF runtime. For tfrt, it is used by fallback op handler.
  virtual void StartStep() = 0;
  // Destroy the step resource container for a training step.
  virtual void EndStep() = 0;

  // Return the Eager Executor for current thread. Please note that Eager

  // If false, all activations are deleted in the first call to ComputeGradient.
  // Else, only when this is destructed.
  bool persistent_;
};

// Describes a callback for special-cased and more efficient jvp computation.
//
// Could just be a simple typedef in ForwardAccumulator, but MSVC chokes on
// that.
template <typename Gradient>
class ForwardFunction