Github user aljoscha commented on the issue:
https://github.com/apache/flink/pull/4616
@pnowojski and @EronWright I changed the name of the `Context`, I added a
test in `StreamSinkOperatorTest`, I added methods or querying current
processing time/watermark to the context. I changed the `timestamp()` method to
return a primitive `long` and I added a method `hasTimestamp()`. Also,
`timestamp()` now throws an exception if no timestamp is available.
What do you think?---
