Hi.
I have a question, regarding fields grouping. In documentation we have:
```
Fields grouping: The stream is partitioned by the fields specified in the
grouping. For example, if the stream is grouped by the "user-id" field,
tuples with the same "user-id" will always go to the same task, but tuples
with different "user-id"'s may go to different tasks.
```
It is clear, when we have single point-to-point connection i.e [A]
--sream--> [B]. But if we have some bolt that consume 2 stream from 2
different bolts but use same key(also streams have same "format") for
fields grouping. Something like this:
```
TopologyBuilder topology = new TopologyBuilder();
// ----
topology.setBolt("alpha", new AlphaBolt(), alphaScaleFactor);
topology.setBolt("beta", new BetaBolt(), betaScaleFactor);
Fields grouping = new Fields("key");
topology.setBolt("gamma", new GammaBolt(), gammaScaleFactor)
.fieldsGrouping("alpha", "alpha-stream", grouping)
.fieldsGrouping("beta", "beta-stream", grouping);
// ----
```
Is there any guarantee that both streams will be partitioned in same way
and tuples with same value in "key" field in both streams will be directed
into same instance/task of "gamma" bolt?
