*value = it->second.value;
    lru_list_.push_front(it->first);
    it->second.lru_iterator = lru_list_.begin();
    return true;
  }

  void InsertLocked(const std::string& key, const T& value)
      ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) {
    lru_list_.push_front(key);
    Entry entry{timer_seconds_(), value, lru_list_.begin()};
    auto insert = cache_.insert(std::make_pair(key, entry));
    if (!insert.second) {

                 absl::Span<const int64_t> shape, const TF_DataType dtype)
      : device_(device),
        tensors_(std::move(tensors)),
        shape_(std::vector<int64_t>(shape.begin(), shape.end())),
        dtype_(dtype) {}
  ParallelTensor(const ParallelDevice& device,
                 std::vector<TensorHandlePtr> tensors, const TF_DataType dtype)
      : device_(device),

    gtl::ArraySlice<Gradient*> output_gradients, absl::Span<Gradient*> result,
    bool build_default_zeros_grads) {
  std::unordered_set<int64_t> sources_set(source_tensor_ids.begin(),
                                          source_tensor_ids.end());
  BackpropInitialState<BackwardFunction, TapeTensor> state = PrepareBackprop(
      target_tensor_ids, tensor_tape_, &op_tape_, sources_set, persistent_);