Show how to use format xtd::format class with std::pair.
#include <xtd/xtd>
#include <utility>
auto main() -> int {
console::out << string::format("{}", key_value_pair(1, "one")) << environment::new_line;
console::out << environment::new_line;
console::out << string::format("{}", std::make_pair(1, "one")) << environment::new_line;
}