error: need ‘typename’ before ‘std::vector<T>::iterator’ because ‘std::vector<T>’ is a dependent scope

template <typename T, typename U>
class Iterator {
public:
    typedef std::vector<T>::iterator iter_type;
    Iterator(U *data, bool reverse = false):data_all(data) {
        m_it = data_all->m_data.begin();
    }
private:
    U *data_all;
    iter_type m_it;

};

./Iter.h:6:13: error: need ‘typename’ before ‘std::vector<T>::iterator’ because ‘std::vector<T>’ is a dependent scope
    6 |     typedef std::vector<T>::iterator iter_type;
      |             ^~~
      |             typename 

typedef typename std::vector<T>::iterator iter_type;