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Hi everyone! I am starting with Kotlin DataFrame. I have a table with a `kotlinx.datetime.Instant` column `timestamp` and would like to add a new column with the difference between the timestamps of the current row and the previous row. It seems I would need something similar to Panda's `diff` operation but I can't find anything  in Kotlin DataFrame documentation. How can I do this?

Hi!
```val timestamp by column&lt;Instant&gt;()
val df = dataFrameOf(timestamp)(
    Instant.fromEpochMilliseconds(1000),
    Instant.fromEpochMilliseconds(3000),
    Instant.fromEpochMilliseconds(5000),
    Instant.fromEpochMilliseconds(3000),
)

val diff  = df.add("diff") { prev()?.let { prev -&gt; it[timestamp] - prev[timestamp] }  }```
It seems we missing an overload for Instant, otherwise it should have worked like this:
```val timestamp by column&lt;Int&gt;()
val df = dataFrameOf(timestamp)(
    1000,
    3000,
    5000,
    3000,
)

val diff  = df.add("diff") { diff { timestamp() }  }
diff.print()```
