Returns:
            the kpoints along the paths in cartesian coordinates
            together with the labels for symmetry points -Wei

def get_kpoints(self, line_density=20, coords_are_cartesian=True):
        """
        Returns:
            the kpoints along the paths in cartesian coordinates
            together with the labels for symmetry points -Wei
        """
        list_k_points = []
        sym_point_labels = []
        for b in self.kpath['path']:
            for i in range(1, len(b)):
                start = np.array(self.kpath['kpoints'][b[i - 1]])
                end = np.array(self.kpath['kpoints'][b[i]])
                distance = np.linalg.norm(
                    self._prim_rec.get_cartesian_coords(start) -
                    self._prim_rec.get_cartesian_coords(end))
                nb = int(ceil(distance * line_density))
                sym_point_labels.extend([b[i - 1]] + [''] * (nb - 1) + [b[i]])
                list_k_points.extend(
                    [self._prim_rec.get_cartesian_coords(start)
                     + float(i) / float(nb) *
                     (self._prim_rec.get_cartesian_coords(end)
                      - self._prim_rec.get_cartesian_coords(start))
                     for i in range(0, nb + 1)])
        if coords_are_cartesian:
            return list_k_points, sym_point_labels
        else:
            frac_k_points = [self._prim_rec.get_fractional_coords(k)
                             for k in list_k_points]
            return frac_k_points, sym_point_labels