def __init__(self):
        super(SaleLine, self).__init__()
        self._order.insert(0, ('sequence', 'ASC'))
        self._error_messages.update({
            'customer_location_required': 'The customer location is required!',
            'missing_account_revenue': 'It misses '
                    'an "Account Revenue" on product "%s"!',
            'missing_account_revenue_property': 'It misses '
                    'an "account Revenue" default property!',
            })