`Primitive` of the super-helical curve.

def curve_primitive(self):
        """`Primitive` of the super-helical curve."""
        curve = self.curve
        curve.axis_start = self.helix_start
        curve.axis_end = self.helix_end
        coords = curve.get_coords(
            n_points=(self.num_monomers + 1), spacing=self.minor_rise_per_residue)
        if self.orientation == -1:
            coords.reverse()
        return Primitive.from_coordinates(coords)