old_contents: from djangotoolbox.auth.models import UserPermissionList, GroupPermissionList, GroupList
  
  def add_to(obj, list_cls, filter):
      obj_list, created = list_cls.objects.get_or_create(**filter)
  
      obj_list.fk_list.append(obj.id)
      obj_list.save()
  
  def add_permission_to_user(perm, user):
      add_to(perm, UserPermissionList,  {'user': user }) 
  
  def add_user_to_group(user, group):
      add_to(group, GroupList, {'user': user})
          
  def add_permission_to_group(perm, group):
      add_to(perm, GroupPermissionList, {'group': group})
  
  def update_permissions_user(perms, user):
      obj_list, created = UserPermissionList.objects.get_or_create(user=user)
  
      old_permissions = list(obj_list.permissions)
      
      for perm in old_permissions:
          try:
              perms.index(perm)
          except ValueError:
              obj_list.fk_list.remove(perm.id)
      
      for perm in perms      :
          try:
              old_permissions.index(perm)
          except ValueError:
              obj_list.fk_list.append(perm.id)
      
      obj_list.save()
  
new_contents: from djangotoolbox.auth.models import UserPermissionList, GroupPermissionList, GroupList
  
  def add_to(obj, list_cls, filter):
      obj_list, created = list_cls.objects.get_or_create(**filter)
  
      obj_list.fk_list.append(obj.id)
      obj_list.save()
  
  def add_permission_to_user(perm, user):
      add_to(perm, UserPermissionList,  {'user': user }) 
  
  def add_user_to_group(user, group):
      add_to(group, GroupList, {'user': user})
          
  def add_permission_to_group(perm, group):
      add_to(perm, GroupPermissionList, {'group': group})
  
  def update_list(objs, list_cls, filter):
      obj_list, created = list_cls.objects.get_or_create(**filter)
  
      old_objs = list(obj_list._get_objs())
      
      for obj in old_objs:
          try:
              objs.index(obj)
          except ValueError:
              obj_list.fk_list.remove(obj.id)
      
      for obj in objs:
          try:
              old_objs.index(obj)
          except ValueError:
              obj_list.fk_list.append(obj.id)
      
      obj_list.save()
      
  def update_permissions_user(perms, user):
      update_list(perms, UserPermissionList, {'user': user})
  
subject: add generic update_list function