ARGOMENTO: ereditare view per rendere campo editabile

<?xml version="1.0"?>
<openerp>
	<data>
		<record model="ir.ui.view" id="view_picking_out_form_weight_free">
			<field name="name">stock.picking.out.form.weight.free</field>
			<!-- <field name="model">product.supplierinfo</field> -->
			<field name="model">stock.picking</field>
			<field name="inherit_id" ref="stock.view_picking_out_form"/>
			<field name="type">form</field> 
			<field name="arch" type="xml">
            	
				<field name="weight" position="replace"/>
				<field name="number_of_packages" position="after">
                	<field name="weight" readonly="0"/>
            	</field>
				
			</field>
		</record>
	</data>
</openerp>

Server Traceback (most recent call last):
  File "/Users/alex/openerp/web/addons/web/common/http.py", line 593, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/Users/alex/openerp/server/openerp/netsvc.py", line 360, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/Users/alex/openerp/server/openerp/service/web_services.py", line 586, in dispatch
    res = fn(db, uid, *params)
  File "/Users/alex/openerp/server/openerp/osv/osv.py", line 167, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/Users/alex/openerp/server/openerp/osv/osv.py", line 121, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/Users/alex/openerp/server/openerp/osv/osv.py", line 176, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/Users/alex/openerp/server/openerp/osv/osv.py", line 164, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/Users/alex/openerp/server/openerp/osv/orm.py", line 2128, in fields_view_get
    arch=apply_view_inheritance(cr, user, source, sql_res['id']),
  File "/Users/alex/openerp/server/openerp/osv/orm.py", line 2086, in apply_view_inheritance
    source = apply_inheritance_specs(source, view_arch, view_id)
  File "/Users/alex/openerp/server/openerp/osv/orm.py", line 2071, in apply_inheritance_specs
    raise_view_error("Element '%s' not found in parent view '%%(parent_xml_id)s'" % tag, inherit_id)
  File "/Users/alex/openerp/server/openerp/osv/orm.py", line 1969, in raise_view_error
    %  (child_view.xml_id, self._name, error_msg))
AttributeError: View definition error for inherited view 'stock_picking_weight_free.view_picking_out_form_weight_free' on model 'stock.picking': Element '<field name="weight">' not found in parent view '%(parent_xml_id)s'

{
    "name" : "Stock picking weight manual",
    "version" : "1.0",
    "author" : "",
    "category" : "Defaults",
    'description': """
        add possibilty to insert weight manually
    """,
    "depends" : ['delivery'],
    "init_xml" : [],
    "demo_xml" : [],
    "update_xml" : ['picking_view.xml'],
    "installable": True,
    "active": True
}