Github user StephanEwen commented on the pull request:
https://github.com/apache/flink/commit/21a715867d655bb61df9a9f7eef37e42b99e206a#commitcomment-15932805
In the current master, the `DataStream` class imports the correct
`o.a.f.api.common.operators.Keys`.
https://github.com/apache/flink/blob/master/flink-streaming-java/src/main/java/org/apache/flink/streaming/api/datastream/DataStream.java#L43
Is it possible that your Maven cache has mixed versions?
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