Function maybe_set_debug_format

include/fmt/format.h:748–751

template <typename Formatter>
FMT_CONSTEXPR auto maybe_set_debug_format(Formatter& f, bool set)
    -> decltype(f.set_debug_format(set)) {
  f.set_debug_format(set);
}
template <typename Formatter>
FMT_CONSTEXPR void maybe_set_debug_format(Formatter&, ...) {}