ARGOMENTO: one2many list

class product_label_epl2_dimension(osv.osv):
    _name = 'product.label.epl2.dimension'
    _description = "Dimensioni etichetta epl2"
    _columns = {
        'name': fields.char('Descrizione', size=100, help="Nome dell'etichetta"),
        'q_label_width': fields.integer('Larghezza etichetta (q)', help="Dimensione area di stampa in dots (12 dots = 1 mm per 300 dpi)"),
        'Q_form_length': fields.char('Lunghezza form (Q)', size=20, help="Lunghezza dell'etichetta di stampa e del gap tra le etichette in dots (12 dots = 1mm per 300 dpi)"),
        'D_density': fields.integer('Densita di stampa (D)', help="Imposta la densita' di stampa"),
        'field_lines': fields.one2many('product.label.epl2.fields', 'dimension_id', 'Campi'),
    }
    _defaults = {
        'q_label_width': 534,
        'Q_form_length': '32,0',
        'D_density': 4,
    }
product_label_epl2_dimension()

class product_label_epl2_fields():
    _name ="product.label.epl2.fields"
    _description = "Campi per le etichette"
    _fonts = (
        (1, '4 pt (12x20 dots)'),
        (2, '6 pt (16x28 dots)'),
        (3, '8 pt (20x36 dots)'),
        (4, '10 pt (24x44 dots'),
        (5, '21 pt (48x80 dots)'),
        ('A', 'Custom font'),
        ('B', 'Custom font'),
        ('C', 'Custom font'),
        ('D', 'Custom font'),
        ('E', 'Custom font'),
    )

    _columns = {
        'dimension_id': fields.many2one('product.label.epl2.dimension', 'Etichetta', select=True),
        'description': fields.char('Descrizione', size=100, help="Semplice descrizione mnemonica del campo"),
        'x': fields.integer('Origine X', help="X coordinata"),
        'y': fields.integer('Origine Y', help="Y coordinata"),
        'font': fields.selection(_fonts, 'Carattere'),
        'campo': fields.many2one('ir.model.fields', 'Campo', on_delete='cascade', domain=[('model', 'like', 'product.%')])
    }
product_label_epl2_fields()

<record id="epl2_dimension_view_form" model="ir.ui.view">
    <field name="name">product.label.epl2.dimension.form</field>
    <field name="model">product.label.epl2.dimension</field>
    <field name="type">form</field>
    <field name="arch" type="xml">
        <form string="Configura Dimensione Etichette">
            <group colspan="4" col="6">
                <field name="name" colspan="6" />
                <field name="q_label_width" colspan="2" />
                <field name="Q_form_heigth" colspan="2" />
                <field name="D_density" colspan="2" />
            </group>
            <notebook colspan="4">
                <page string="Campi">
                    <field mode="form,tree" name="field_lines" nolabel="1" widget="one2manylist" colspan="4" >
                        <form string="Campi Etichetta">
                            <group col="6" colspan="4">
                                <field name="description" colspan="6" />
                                <field name="x" colspan="2" />
                                <field name="y" colspan="2" />
                                <field name="font" colspan="2" />
                                <field name="campo" colspan="6" />
                            </group>
                        </form>
                        <tree string="Campi etichetta">
                            <field name="description" />
                            <field name="x" />
                            <field name="y" />
                            <field name="font" />
                            <field name="campo" />
                        </tree>
                    </field>
                </page>
            </notebook>
        </form>
    </field>
</record>

Client Traceback (most recent call last):
  File "/opt/openerp/openerp6.1/web/addons/web/common/http.py", line 180, in dispatch
    response["result"] = method(controller, self, **self.params)
  File "/opt/openerp/openerp6.1/web/addons/web/controllers/main.py", line 1209, in load
    return self.fields_view_get(req, model, view_id, view_type, toolbar=toolbar)
  File "/opt/openerp/openerp6.1/web/addons/web/controllers/main.py", line 1091, in fields_view_get
    fvg = Model.fields_view_get(view_id, view_type, context, toolbar, submenu)
  File "/opt/openerp/openerp6.1/web/addons/web/common/openerplib/main.py", line 250, in proxy
    args, kw)
  File "/opt/openerp/openerp6.1/web/addons/web/common/openerplib/main.py", line 117, in proxy
    result = self.connector.send(self.service_name, method, *args)
  File "/opt/openerp/openerp6.1/web/addons/web/common/http.py", line 608, in send
    raise xmlrpclib.Fault(openerp.tools.exception_to_unicode(e), formatted_info)


Server Traceback (most recent call last):
  File "/opt/openerp/openerp6.1/web/addons/web/common/http.py", line 593, in send
    return openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/opt/openerp/openerp6.1/server/openerp/netsvc.py", line 360, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/opt/openerp/openerp6.1/server/openerp/service/web_services.py", line 586, in dispatch
    res = fn(db, uid, *params)
  File "/opt/openerp/openerp6.1/server/openerp/osv/osv.py", line 167, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/opt/openerp/openerp6.1/server/openerp/osv/osv.py", line 121, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/opt/openerp/openerp6.1/server/openerp/osv/osv.py", line 176, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/opt/openerp/openerp6.1/server/openerp/osv/osv.py", line 164, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/opt/openerp/openerp6.1/server/openerp/osv/orm.py", line 2153, in fields_view_get
    xarch, xfields = self.__view_look_dom_arch(cr, user, result['arch'], view_id, context=ctx)
  File "/opt/openerp/openerp6.1/server/openerp/osv/orm.py", line 1793, in __view_look_dom_arch
    fields_def = self.__view_look_dom(cr, user, node, view_id, False, fields, context=context)
  File "/opt/openerp/openerp6.1/server/openerp/osv/orm.py", line 1742, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, view_id, in_tree_view, model_fields, context))
  File "/opt/openerp/openerp6.1/server/openerp/osv/orm.py", line 1742, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, view_id, in_tree_view, model_fields, context))
  File "/opt/openerp/openerp6.1/server/openerp/osv/orm.py", line 1742, in __view_look_dom
    fields.update(self.__view_look_dom(cr, user, f, view_id, in_tree_view, model_fields, context))
  File "/opt/openerp/openerp6.1/server/openerp/osv/orm.py", line 1661, in __view_look_dom
    xarch, xfields = relation.__view_look_dom_arch(cr, user, f, view_id, ctx)
AttributeError: 'NoneType' object has no attribute '_BaseModel__view_look_dom_arch'