const std::string& UrlQuery::Get(const std::string& key) const {
  auto it = Find(key);
  if (it != parameters_.end()) {
    return it->second;
  }

  static const std::string kEmptyValue;
  return kEmptyValue;
}
const std::string& UrlQuery::Get(const std::string& key) const {
  auto it = Find(key);
  if (it != parameters_.end()) {
    return it->second;
  }

  static const std::string kEmptyValue;
  return kEmptyValue;
}