@Override
    public String buildContext() {
        final String selector = ((Collection<?>) getSource())
                .stream()
                .map(s -> ((RuleDO) s).getName())
                .collect(Collectors.joining(","));
        final String namespaceId = ((Collection<?>) getSource())
                .stream()
                .filter(s -> StringUtils.isNotEmpty(((RuleDO) s).getNamespaceId()))
                .map(s -> ((RuleDO) s).getNamespaceId())
                .findAny().orElse(SYS_DEFAULT_NAMESPACE_ID);
        return String.format("the namespace [%s] rule[%s] is %s", namespaceId, selector, StringUtils.lowerCase(getType().getType().toString()));
    }
Create a new {@code BatchChangedEvent}.operator is unknown.

@param source   Current plugin state
@param operator operator
@param plugins  about plugin
shenyu-admin/src/main/java/org/apache/shenyu/admin/model/event/rule/BatchRuleDeletedEvent.java