I am unsuccesfully trying to inherit by delegation from model res.parter the same way res.user does as it can be seen in https://github.com/odoo/odoo/blob/8.0/openerp/addons/base/res/res_users.py#L143-L145 , I am getting the following error from the following sample model

My model:

# -*- coding: utf-8 -*-
from openerp import fields
from openerp import models

class Example (models.Model):
    _name = 'example.prueba'
    _inherits = {
        'res.partner': 'partner_id',
    }

    sample_field = fields.Char(string="Field")

The error:

Traceback (most recent call last):

  File "/usr/lib/python2.7/dist-packages/werkzeug/serving.py", line 177, in run_wsgi

    execute(self.server.app)

  File "/usr/lib/python2.7/dist-packages/werkzeug/serving.py", line 165, in execute

    application_iter = app(environ, start_response)

  File "/usr/lib/python2.7/dist-packages/openerp/service/server.py", line 281, in app

    return self.app(e, s)

  File "/usr/lib/python2.7/dist-packages/openerp/service/wsgi_server.py", line 216, in application

    return application_unproxied(environ, start_response)

  File "/usr/lib/python2.7/dist-packages/openerp/service/wsgi_server.py", line 202, in application_unproxied

    result = handler(environ, start_response)

  File "/usr/lib/python2.7/dist-packages/openerp/http.py", line 1239, in __call__

    return self.dispatch(environ, start_response)

  File "/usr/lib/python2.7/dist-packages/openerp/http.py", line 1213, in __call__

    return self.app(environ, start_wrapped)

  File "/usr/lib/python2.7/dist-packages/werkzeug/wsgi.py", line 588, in __call__

    return self.app(environ, start_response)

  File "/usr/lib/python2.7/dist-packages/openerp/http.py", line 1371, in dispatch

    ir_http = request.registry['ir.http']

  File "/usr/lib/python2.7/dist-packages/openerp/http.py", line 331, in registry

    return openerp.modules.registry.RegistryManager.get(self.db) if self.db else None

  File "/usr/lib/python2.7/dist-packages/openerp/modules/registry.py", line 315, in get

    update_module)

  File "/usr/lib/python2.7/dist-packages/openerp/modules/registry.py", line 346, in new

    openerp.modules.load_modules(registry._db, force_demo, status, update_module)

  File "/usr/lib/python2.7/dist-packages/openerp/modules/loading.py", line 365, in load_modules

    registry.setup_models(cr)

  File "/usr/lib/python2.7/dist-packages/openerp/modules/registry.py", line 174, in setup_models

    model._setup_fields(cr, SUPERUSER_ID, partial=partial)

  File "/usr/lib/python2.7/dist-packages/openerp/api.py", line 237, in wrapper

    return old_api(self, *args, **kwargs)

  File "/usr/lib/python2.7/dist-packages/openerp/api.py", line 332, in old_api

    result = method(recs, *args, **kwargs)

  File "/usr/lib/python2.7/dist-packages/openerp/models.py", line 2971, in _setup_fields

    field.setup(self.env)

  File "/usr/lib/python2.7/dist-packages/openerp/fields.py", line 411, in setup

    self._setup(env)

  File "/usr/lib/python2.7/dist-packages/openerp/fields.py", line 417, in _setup

    self._setup_related(env)

  File "/usr/lib/python2.7/dist-packages/openerp/fields.py", line 449, in _setup_related

    field = recs._fields[name]

KeyError: 'partner_id'

any help would be appreciated, thanks.