@Override
    public Map<String, String> contextLabels() {
        return Collections.unmodifiableMap(contextLabels);
    }
@Test
    public void testCreationWithValidNamespaceAndNullLabelValues() {
        labels.put(LABEL_A_KEY, null);
        context = new KafkaMetricsContext(namespace, labels);

        assertEquals(2, context.contextLabels().size());
        assertEquals(namespace, context.contextLabels().get(MetricsContext.NAMESPACE));
        assertNull(context.contextLabels().get(LABEL_A_KEY));
    }