public ConsumerFilterData get(final String topic, final String consumerGroup) {
        if (!this.filterDataByTopic.containsKey(topic)) {
            return null;
        }
        if (this.filterDataByTopic.get(topic).getGroupFilterData().isEmpty()) {
            return null;
        }

        return this.filterDataByTopic.get(topic).getGroupFilterData().get(consumerGroup);
    }
@Test
    public void testPersist() {
        ConsumerFilterManager filterManager = gen(10, 10);

        try {
            filterManager.persist();

            ConsumerFilterData filterData = filterManager.get("topic9", "CID_9");

            assertThat(filterData).isNotNull();
            assertThat(filterData.isDead()).isFalse();

            ConsumerFilterManager loadFilter = new ConsumerFilterManager();

            assertThat(loadFilter.load()).isTrue();

            filterData = loadFilter.get("topic9", "CID_9");

            assertThat(filterData).isNotNull();
            assertThat(filterData.isDead()).isTrue();
            assertThat(filterData.getCompiledExpression()).isNotNull();
        } finally {
            UtilAll.deleteFile(new File("./unit_test"));
        }
    }