def METHOD_NAME(model, update_model, _model_context):
    """
    Ensure that the AdminServerName attribute is set, and that the server is defined.
    This is required by WKO 3.0, and not by 4.0 and later.
    :param model: the model to be filtered
    :param update_model: the model to be updated with any changes
    :param _model_context: unused, passed by filter_helper if called independently
    """
    _method_name = 'check_admin_server_defined'
    target_key = _model_context.get_target_configuration().get_product_key()
    topology_folder = dictionary_utils.get_dictionary_element(model, TOPOLOGY)
    admin_server_name = dictionary_utils.get_element(topology_folder, ADMIN_SERVER_NAME)
    if not admin_server_name:
        admin_server_name = DEFAULT_ADMIN_SERVER_NAME
        _logger.info('WLSDPLY-20206', ADMIN_SERVER_NAME, admin_server_name, target_key, class_name=_class_name,
                     method_name=_method_name)
        update_topology_folder = _get_folder(update_model, TOPOLOGY)
        update_topology_folder[ADMIN_SERVER_NAME] = admin_server_name
    servers_folder = dictionary_utils.get_dictionary_element(topology_folder, SERVER)
    if admin_server_name not in servers_folder:
        _logger.info('WLSDPLY-20207', SERVER, admin_server_name, target_key, class_name=_class_name,
                     method_name=_method_name)
        update_servers_folder = _get_folder(update_model, TOPOLOGY, SERVER)
        update_servers_folder[admin_server_name] = PyOrderedDict()