constexpr auto _element_at_cart_prod_result_seq(CartProdT &&t, SubsTupleT &&subs, const const_ints<size_t, Is...> &) { return as_tuple( element_at_index(std::get<Is>(t.inputs), std::get<Is>(subs))...); }
PyObject * apply_to(T & x) { x.serialize(*this,0); return as_tuple();}