code: def is_autoshape(self):
          
          prstGeom = self.prstGeom
          if prstGeom is None:
              return False
          if self.nvSpPr.cNvSpPr.txBox is True:
              return False
          return True
docs: True if this shape is an auto shape. A shape is an auto shape if it
          has a ``<a:prstGeom>`` element and does not have a txBox="1" attribute
          on cNvSpPr.