How do I retrieve members (id) from a contact list using Eloqua REST API

I am trying to retrieve member (id) from Elouqa  Contact List (given contact list id), using Eloqua REST API.

Another related question. I am trying to update eloqua contact list with members. I have a new list of members that should be added to the existing Eloqua contact list, if they are not already there. Any member that is currently in the Eloqua contact list, but not in my new list should be deleted.

using REST API,

PUT /assets/contact/list/{id}

I can use "membershipaddiitons" field to add more members. My problem is that I don't know what member is current there, So I cannot use "membershipdeletions" field to delete unwanted members from a contact list.

So I need to have a way to retrieve existing member IDs from a contact list.