how to get topic names in SinkFunction when using FlinkKafkaConsumer010 with multiple topics

[Richard Xin]

when using FlinkKafkaConsumer010 to subscribing multiple topics as 
List<String> topics = Arrays.asList("test1","test2");
DataStream<String> stream = env.addSource(new FlinkKafkaConsumer010<>(topics, 
new SimpleStringSchema(), properties));
How do I get topic names in my SinkFunction? i.e. stream.addSink()
Thanks,Richard