@Override
    public boolean contains(String clientId) {
        return clients.containsKey(clientId);
    }
@Test
    void testContains() {
        assertTrue(persistentIpPortClientManager.contains(clientId));
        String unUsedClientId = "127.0.0.1:8888#true";
        assertFalse(persistentIpPortClientManager.contains(unUsedClientId));
    }