if (currentList != null) {
                    throw new UnsupportedOperationException("<dl> within a <dl> is not supported.");
                }
                currentList = document.createElement("variablelist");
                nodes.push(currentList);
                return true;
            }
            if (elementName.equals("dt")) {
                if (currentItem != null) {
                    nodes.pop();

    return nullptr;
  }
  const auto& m = reader->GetVariableToDataTypeMap();
  for (auto it = m.begin(); it != m.end(); ++it)
    reader->variable_list.push_back(it->first);
  std::sort(reader->variable_list.begin(), reader->variable_list.end());
  return reader;
}

void TF_DeleteCheckpointReader(TF_CheckpointReader* reader) { delete reader; }