// Check if election has been won
bool won = print_winner();
t appears that the above code as part of the main function will remain as it is since there is no mention of TO DO.
My understanding is that the brackets denoting void with print_winner() should give the name of winner candidate as output here if won = true. And that name of winner is coming from print_winner function.
Although from the current code, getting name of winner candidate as output, unable to figure out the reason behind the error message.