I needed to change some attributes of the 'stock.move' popup screen that opened when one need to add a product in a delivery order screen, I added the following code

    def fields_view_get(self, cr, uid, view_id=None, view_type='form', context=None, toolbar=False, submenu=False):
        if context is None:
            context = {}
        res = super(stock_move, self).fields_view_get(cr, uid, view_id, view_type, context, toolbar=toolbar, submenu=submenu)
        if context.get('picking_type') and context['picking_type']=='out':
            doc = etree.XML(res['arch'])
            domain ="[('use_type','=','finished')]"
            nodes = doc.xpath("//field[@name='product_id']")
            for node in nodes:
                node.set('domain', domain)
                node.set('string', 'Finished Product')
            nodes2 = doc.xpath("//field[@name='prodlot_id']")
            for node in nodes2:
                node.set('readonly',"1")
                node.set('invisible',"1")
                node.set('string',"1==================")                
            res['arch'] = etree.tostring(doc)

The first nodes loop worked ok, the second one, nodes2, didn't work, i.e, the field still available and editable. I added the last line for test and for surprise it worked. Any idea is appreciated