docs: public Collection<TopicPartition> getTopicPartitions() {
          Collection<TopicPartitionGroup> topicPartitions = getTopicPartitionGroups();
          Set<TopicPartition> tps = new HashSet<TopicPartition>();
          if (topicPartitions != null) {
              for (TopicPartitionGroup g : topicPartitions) {
                  tps.addAll(g.getTopicPartitions());
              }
          }
          return tps;
      }