*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) {

void Close(const TF_WritableFile* file, TF_Status* status);
}  // namespace tf_writable_file

namespace tf_read_only_memory_region {
void Cleanup(TF_ReadOnlyMemoryRegion* region);
const void* Data(const TF_ReadOnlyMemoryRegion* region);
uint64_t Length(const TF_ReadOnlyMemoryRegion* region);
}  // namespace tf_read_only_memory_region

namespace tf_gcs_filesystem {
typedef struct GcsFileStat {
  TF_FileStatistics base;
  int64_t generation_number;

                 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),

// completed. The memory returned might alias the internal memory used by
// TensorFlow. Hence, callers should not mutate this memory (for example by
// modifying the memory region pointed to by TF_TensorData() on the returned
// TF_Tensor).
TF_CAPI_EXPORT extern TF_Tensor* TFE_TensorHandleResolve(TFE_TensorHandle* h,
                                                         TF_Status* status);

    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_);

                              const TF_ReadOnlyMemoryRegionOps* ops)
      : region_(std::move(region)), ops_(ops) {}

  ~ModularReadOnlyMemoryRegion() override { ops_->cleanup(region_.get()); };

  const void* data() override { return ops_->data(region_.get()); }
  uint64 length() override { return ops_->length(region_.get()); }

 private:

  ops->writable_file_ops_size = TF_WRITABLE_FILE_OPS_SIZE;
  ops->read_only_memory_region_ops_abi = TF_READ_ONLY_MEMORY_REGION_OPS_ABI;
  ops->read_only_memory_region_ops_api = TF_READ_ONLY_MEMORY_REGION_OPS_API;
  ops->read_only_memory_region_ops_size = TF_READ_ONLY_MEMORY_REGION_OPS_SIZE;
}

/// Initializes a TensorFlow plugin.
///