public boolean valid() {
        return accessKey != null && !accessKey.isEmpty() && secretKey != null && !secretKey.isEmpty();
    }
@Test
    void testValid() {
        //given
        String ak = "ak";
        String sk = "sk";
        String tenantId = "100";
        Credentials credentials = new Credentials(ak, sk, tenantId);
        //when
        boolean actual = credentials.valid();
        //then
        assertTrue(actual);
    }