code: def add_freeform_sp(self, x, y, cx, cy):
          
          shape_id = self._next_shape_id
          name = 'Freeform %d' % (shape_id-1,)
          sp = CT_Shape.new_freeform_sp(shape_id, name, x, y, cx, cy)
          self.insert_element_before(sp, 'p:extLst')
          return sp
docs: Append a new freeform `p:sp` with specified position and size.