@Override
    public Map<String, String> contextLabels() {
        return Collections.unmodifiableMap(contextLabels);
    }
Create a MetricsContext with namespace, service or client properties
@param namespace value for _namespace key
@param contextLabels  contextLabels additional entries to add to the context.
                 values will be converted to string using Object.toString()
clients/src/main/java/org/apache/kafka/common/metrics/KafkaMetricsContext.java