I would like to know how to get the returned value from a Promise. I override the JS method for ListController so that the Action button menu list will be overridden according to some condition.

Here's my code:

odoo.define('custom_contacts.ListController', function (require) {

    "use strict";    
    var core = require('web.core');
    var ListController = require('web.ListController')
    var rpc = require('web.rpc')
    var Sidebar = require('web.Sidebar');    

    var _t = core._t;
    ListController.include({
            renderSidebar: function($node) {
                var self = this;
                var user_group = this._get_user_group()
                var group_admin
                Promise.resolve(user_group).then(function(value){
                       console.log(value)
                       group_admin = value
                })
                console.log(group_admin)                  

if (this.hasSidebar && group_admin) {

 //if group_admin is true then show export, archive, unarchive menu in action button
      var other = [{
          label: _t("Export"),
          callback: this._onExportData.bind(this)
      }];

      if (this.archiveEnabled) {
         other.push({
              label: _t("Archive"),
              callback: function () {
                 Dialog.confirm(self, _t("Are you sure that you want to archive all the selected records?"), {
                       confirm_callback: self._onToggleArchiveState.bind(self, true),
                 }); 
              }
          });

         other.push({ 
              label: _t("Unarchive"),
              callback: this._onToggleArchiveState.bind(this, false)
         });

     }
     if (this.is_action_enabled('delete')) {
         other.push({
              label: _t('Delete'),
              callback: this._onDeleteSelectedRecords.bind(this)
         });
     }
     this.sidebar = new Sidebar(this, {
          editable: this.is_action_enabled('edit'),
          env: {
               context: this.model.get(this.handle, {raw: true}).getContext(),
               activeIds: this.getSelectedIds(),
               model: this.modelName,
          },
          actions: _.extend(this.toolbarActions, {other: other}),
     });     
     this.sidebar.appendTo($node); 

     this._toggleSidebar();

} else {
// show export in action button only
      var other = [{
          label: _t("Export"),
          callback: this._onExportData.bind(this)
      }]; 

      this.sidebar = new Sidebar(this, {
            editable: this.is_action_enabled('edit'),
            env: { 
                  context: this.model.get(this.handle, {raw: true}).getContext(),
                  activeIds: this.getSelectedIds(),
                  model: this.modelName,
            },
            actions: _.extend(this.toolbarActions, {other: other}),
      });

      this.sidebar.appendTo($node); 

      this._toggleSidebar();
}  

}, 
_get_user_group: function(){
      return rpc.query({
          model: 'res.partner', 
          method: 'get_current_user_group',
          args: [{}]
      }).then(function(data) {     
            //data is either true or false
            return data
      })
 },

});     

return ListController;
});

    

I always get undefined value in console.log(group_admin), however inside the .then() function value returned from the model is displayed correctly. Maybe I'm not doing it correctly. Any help will be greatly appreciated.. Thanks