code: public function getGroupMenu($group_id)
      {
          $map = [
              'id' => $group_id
          ];
          $group = $this->model->field('group_menus')
              ->where($map)
              ->find();
          if ($group && $group['group_menus']) {
              return explode(',', $group['group_menus']);
          }
          return [];
      }
docs: 群组菜单
  
  @param number $group_id
  @return array