Your method should return an action, something like this:

 return {
                'name': _(u"Eventos Eletrônicos"),
                'view_mode': 'form',
                'view_id': view[1],
                'view_type': 'form',
                'res_model': 'l10n_br_account.document_event',
                'res_id': last_event,
                'type': 'ir.actions.act_window',
                'nodestroy': True,
                'target': 'new',
                'domain': '[]',
                'context': None
            }

Existing Object/Button ?