Hello everybody,

I am using the Kapacitor to get the duration of a state with the node StateDurationNode.

For example the input raw data data is:
| timestamp [s] | value [boolean] |
|---|---|
0 | FALSE
1 | TRUE
2 | TRUE
3 | TRUE
4 | TRUE
5 | FALSE
6 | FALSE

The expected result is:
| timestamp [s] | value [s] |
|-|-|
1 | 3

The current result is:
| timestamp [s] | value [s] |
|-|-|
2 | 1
3 | 2
4 | 3
Source code:
```
stream
    |from()
        .measurement('data')
    |stateDuration(lambda: "state" == TRUE)
        .unit(1s)
        .quiet()
        .as('durations')
    |httpOut('duration')
    |influxDBOut()
        .database('test')
        .measurement('durations')
```

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