Function insert

include/boost/parser/parser.hpp:1458–1465

        template<typename Container, typename T>
        void insert(Container & c, T && x)
        {
            if constexpr (is_detected_v<has_push_back, Container>) {
                c.push_back((T &&) x);
            } else {
                c.insert((T &&) x);
            }
        }

        template<typename Container, typename I>
        void insert(Container & c, I first, I last)