Return new `p:sp` element tree configured as freeform shape.

        The returned shape has a `a:custGeom` subtree but no paths in its
        path list.

def new_freeform_sp(shape_id, name, x, y, cx, cy):
        """Return new `p:sp` element tree configured as freeform shape.

        The returned shape has a `a:custGeom` subtree but no paths in its
        path list.
        """
        tmpl = CT_Shape._freeform_sp_tmpl()
        xml = tmpl % (shape_id, name, x, y, cx, cy)
        sp = parse_xml(xml)
        return sp