Method map_or

extlibs/sol3/include/sol/sol.hpp:4342–4344

		/// \group map_or
		template <class F, class U>
		U map_or(F&& f, U&& u) & {
			return has_value() ? detail::invoke(std::forward<F>(f), **this) : std::forward<U>(u);
		}

		/// \group map_or
		template <class F, class U>