proteus change draft sale state

CODE

#!/usr/bin/env python
# -*- coding: utf8 -*-

#Try to quote draft sale

from proteus import config, Model
from con_data_dm import *

config = config.set_xmlrpc(url)

Sale = Model.get('sale.sale')
(sale,) = Sale.find([('id','=',"2456")])
Sale.quote([sale.id], config.context)



RESULT

Traceback (most recent call last):
  File "change_sale_state.py", line 13, in <module>
    Sale.quote([sale.id], config.context)
AttributeError: type object 'sale.sale' has no attribute 'quote'