@Override
    @ManagedOperation(description = "Does the store contain the given key")
    public boolean contains(String key) {
        return this.cache.containsKey(key);
    }
@Test
    void testContains() {
        assertFalse(repo.contains(key01));

        // add key and check again
        assertTrue(repo.add(key01));
        assertTrue(repo.contains(key01));

    }