std::unordered_map<std::string, std::string> props(properties.cbegin(), properties.cend());
#if __cplusplus >= 201703L
props.merge(properties_);
std::unordered_map<std::string, std::string> props(properties.cbegin(), properties.cend());
#if __cplusplus >= 201703L
props.merge(properties_);