I need to add EAN field on "Recieve product" form.

I'm trying to inherit stock_partial_picking_line class, with using my extra module.

Model:

from openerp.osv import fields, osv
class stock_partial_picking_line(osv.TransientModel):
_name = "stock.partial.picking.line"
_rec_name = "product_id"
_inherit = "stock.partial.picking.line"

_columns = {
    'product_id_ean13': fields.related('product_id', 'ean13', type='char', string='EAN'),
}

View:

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
        <!-- this view of stock.partial.picking wizard is dedicated to internal picking. The fields_view_get is ovveridden in order to change the label of the process button and the separator. -->
        <record id="stock_partial_picking_form" model="ir.ui.view">
            <field name="name">stock.partial.picking.form</field>
            <field name="model">stock.partial.picking</field>
            <field name="inherit_id" ref="stock.stock_partial_picking_form"/>
            <field name="arch" type="xml">
                <field name="product_id" position="before">
                    <field name="product_id_ean13"/>
                </field>
            </field>
        </record>

    </data>
</openerp>

But when I'm trying to open form, getting the following error message:

Can't find field 'product_id_ean13' in the following view parts composing the view of object model 'stock.partial.picking': * stock.partial.picking.form

What I'm doing wrong?