Sorry ! I have been completely wrong where i should place the filter 
Just received the other day proper instructions about where it should be placed and now it works, but i just need to translate what i’m showing and implement the filter function as the error that shows a message like "NotImplementedError: Missing the search function of field “Período de agrupación de facturas de ventas” (“Sale Invoice Grouping Period”).
from trytond.pool import PoolMeta
from trytond.model import ModelSQL, fields
from trytond.pool import Pool
class SaleAccountInvoiceGroupingMethod(metaclass=PoolMeta):
'Party Sales Period Searcher and tree view'
__name__ = 'account.invoice'
sale_period = fields.Function(fields.Char('Sale Period', help="This is a test"), **# how to translate help tool in local .po ?**
getter='get_periods',
searcher='searcher_sale_period')
@classmethod
def searcher_sale_period(cls, name, clause):
return [
('party.sale_invoice_grouping_period', clause[1], clause[2])
]
def get_periods(self, name):
if self.party.sale_invoice_grouping_method == 'standard':
return self.party.sale_invoice_grouping_period
return 'None'
The thing is that i’m seeing the default language and not the translatiosn for each period. Seen this post and it looks that it should be done like this ?If somebody can explain me a little bit more how this works if so ? https://discuss.tryton.org/t/how-to-get-fields-translations/2339?u=daniel_dev
And thought that if i’m allready doing thranslatios for Sale Peridos i also should do the same for “Payment Days” (i’ve just created a pull request on git-hub- trytond-account_payment_days ) as it’s not translated. Any help would be appreciated!