'Return true if the current user has permission on the page.
Return the string \'All\' if the user has all rights.'

def has_change_permission(self, request, obj=None):

    if obj:
        return page_permissions.user_can_change_page(request.user, page=obj)
    can_change_page = page_permissions.user_can_change_at_least_one_page(user=request.user, site=current_site(request), use_cache=False)
    return can_change_page
