good day everyone,  I'm working on 13 community. I've been hitting my head against the wall trying to figure how to add simple field to customer. please anyone that can point me the proper direction.

 .py is:

class ResPartner(models.Model):
    _inherit = 'res.partner'

    partner_custref = fields.Char(string="Referencia Cliente2")

and throws this error:

psycopg2.errors.UndefinedColumn: column res_partner.partner_custref does not exist