Return `p:grpSp` element newly appended to this shape tree.

        The element contains no sub-shapes, is positioned at (0, 0), and has
        width and height of zero.

def add_grpSp(self):
        """Return `p:grpSp` element newly appended to this shape tree.

        The element contains no sub-shapes, is positioned at (0, 0), and has
        width and height of zero.
        """
        shape_id = self._next_shape_id
        name = 'Group %d' % (shape_id-1,)
        grpSp = CT_GroupShape.new_grpSp(shape_id, name)
        self.insert_element_before(grpSp, 'p:extLst')
        return grpSp