I have an option that is a std::tuple<double, double, double, double> type.
When I call App::config_to_str the tuple option is not being written to the config string because its string representation is empty.
I am, however, able to use the option in the config file, so I know the to/from string steps are working everywhere except in config_to_str.

I am using 1.9.0 and I see that 1.9.1 has a string conversion fix, #421, but I do not know if that fix also addresses tuple problems like this.

Thanks for make CLI11 a great library for the rest of us to use! (I have bugged you in the past from account @pwm1234)
Phil