from odoo import models, fields, api, _, Command


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

    billing_contacts = fields.Many2many(string='Default Billing Contacts',
                                        comodel_name='res.partner',
                                        compute='_compute_billing_contacts',
                                        inverse='_inverse_billing_contacts')

    @api.depends('child_ids.type')
    def _compute_billing_contacts(self):
        for rec in self:
            rec.billing_contacts = rec.child_ids.filtered(lambda r: r.type == 'invoice')

    @api.depends('billing_contacts')
    def _inverse_billing_contacts(self):
        for partner in self.mapped('billing_contacts'):
            partner.type = 'invoice'