[tryton] How to use Wizard product.by_location with proteus on Tryton 2.8

[TPH]

Hello,

I try to get the stock and the locations of a product but can't get it work.




#!/usr/bin/env python
#-*- coding: utf-8 -*-


import datetime
from proteus import config, Model, Wizard
from con_data import *
config = config.set_xmlrpc(url)


Product = Model.get('product.product')
Location = Model.get('stock.location')
Inventory = Model.get('stock.inventory')

locations = Location.find([('type', '=', 'storage'), ('parent.name', '=' ,'Main 
Storage')])
locations = [l.id for l in locations]

config.context['language'] = 'de_DE'
config._context['locations'] = locations
#config.context['stock_date_end'] = datetime.date(2015, 4, 7) 

def check_stock(product_code):
    (product,) = Product.find([('code', '=', product_code)])
    print "product code:", product.code
    print "product name:", product.name
    print "product quantity:", product.quantity
    bylocation  = Wizard('product.by_location', [product])
    bylocation.execute("by_location")

check_stock("PRODUCTCODE")




    assert state in self.states
AssertionError



I have never used state and have no clue how to use it. Would be nice to 
get some help.
I have the correct stock but cant find the storage name.

Thanks