code: def add_grpSp(self):
          
          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
docs: 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.