lru_list_.erase(insert.first->second.lru_iterator);
      insert.first->second = entry;
    } else if (max_entries_ > 0 && cache_.size() > max_entries_) {
      cache_.erase(lru_list_.back());
      lru_list_.pop_back();
    }
  }

  bool DeleteLocked(const std::string& key) ABSL_EXCLUSIVE_LOCKS_REQUIRED(mu_) {
    auto it = cache_.find(key);
    if (it == cache_.end()) {
      return false;
    }

    tensor_stack.push_back(t);
  }
  BackpropInitialState<BackwardFunction, TapeTensor> result;
  while (!tensor_stack.empty()) {
    int64_t tensor_id = tensor_stack.back();
    tensor_stack.pop_back();
    auto op_id_it = tensor_tape.find(tensor_id);
    if (op_id_it == tensor_tape.end()) {
      continue;
    }
    int64_t op_id = op_id_it->second;
    auto op_it = op_tape->find(op_id);

    rng_val_ = distribution(gen);
  }

  static void SetCloudPath(const std::string& cloud_path) {
    cloud_path_ = cloud_path;
    if (cloud_path_.back() == '/') cloud_path_.pop_back();
  }

  static void SetTmpDir(const std::string& tmp_dir) {
    tmp_dir_ = tmp_dir.empty() ? ::testing::TempDir() : tmp_dir;
  }

 protected:
  Env* env_;

 private: