Method operator()

Source/Utils/json.hpp:4350–4354

        {
            template<typename BasicJsonType, typename T>
            auto operator()(BasicJsonType& j, T&& val) const noexcept(noexcept(to_json(j, std::forward<T>(val))))
                -> decltype(to_json(j, std::forward<T>(val)), void())
            {
                return to_json(j, std::forward<T>(val));
            }
        };
    }  // namespace detail