@Override
        public Map<String, SystemStreamMetadata> apply() {
          throw new SamzaException("Failed to get system stream metadata");
        }
Given a set of stream names (topics), fetch metadata from Kafka for each
stream, and return a map from stream name to SystemStreamMetadata for
each stream. This method will return null for oldest and newest offsets
if a given SystemStreamPartition is empty. This method will block and
retry indefinitely until it gets a successful response from Kafka.

@param streamNames a set of strings of stream names/topics
@param retryBackoff retry backoff strategy
@return a map from topic to SystemStreamMetadata which has offsets for each partition
samza-kafka/src/main/java/org/apache/samza/system/kafka/KafkaSystemAdmin.java