I have connected res_users and res_partner with a many2many relation, so every user has his contacts that he is responsible for and a contact can be in different users.

My problem is that I can't figure out how to get all res_partner ids that are in relation with a user. I need this in a website so it needs to work in a controller. That's why I can't just query it. Can someone help me with this? I need only ids of the partners so I can use that in a search([('partner_id', 'IN', users_contact_ids)])

# Field in res.users model
res_partner_ids = fields.Many2many('res.partner',
                                       relation='res_users_partners_rel',
                                       column1='res_users_id',
                                       column2='res_partner_id',
                                       string='Contacts on user')