openerp - QWebException: "'NoneType' object has no attribute 'with_context'" while evaluating "doc.with_context({'lang':doc.partner_id.lang})" -

i new odoo, created module inheriting sales_order create custom report. getting above error when printing report. need please?

here code snippets:

test/my_module.py:

class sale_order(models.model):    _name = 'sale.order'    _description = 'inheritance'   _inherit = 'sale.order' 

test/views/report_template_view.xml:

<?xml version="1.0" encoding="utf-8"?>     <openerp>         <data>             <template id="test_report">                 <t t-call="report.html_container">                  <t t-call="report.internal_layout">                  <t t-set="doc" t-value="doc.with_context({'lang':doc.partner_id.lang})"/>                  <div class="page">                      <div class="oe_structure"/>                          <div> <strong><left>user</left></strong>                              <p t-field="doc.user_id"/>                          </div>                       </div>              </t>             </t>    </template> </data> 

how can access records in custom_report_template?

i know i'm late name of variable containing recordset passed template docs not doc. , trying value variable don't have anything.

doc.with_context({'lang':doc.partner_id.lang}) 

i think need docs not doc because doc none why template in loop docs :

   <t t-foreach="docs" t-as="o">