: AbstractContext(kind) {}
  ~ImmediateExecutionContext() override {}
};

namespace internal {
struct ImmediateExecutionContextDeleter {
  void operator()(ImmediateExecutionContext* p) const {
    if (p != nullptr) {
      p->Release();
    }
  }
};
}  // namespace internal

using ImmediateContextPtr =
    std::unique_ptr<ImmediateExecutionContext,

void ForwardAccumulator<Gradient, BackwardFunction, TapeTensor>::Watch(
    int64_t tensor_id, Gradient* tangent) {
  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 {