rowwise misses the first group and can not be printed

[holgerbrandl]

Example

 val lambdas = (1..3).map { 0.25 }.cumSum()
    val mus = (1..3).map { 0.25 }.cumSum()

 fun <A, B> cartesianProduct(
    listA: Iterable<A>,
    listB: Iterable<B>
): Sequence<Pair<A, B>> =
    sequence {
        listA.forEach { a ->
            listB.forEach { b ->
                yield(a to b)
            }
        }
    }
cartesianProduct(lambdas, mus).map { mapOf("lambda" to it.first, "mu" to it.second) }

var df = dataFrameOf(cartesianProduct(lambdas, mus).map { mapOf("lambda" to it.first, "mu" to it.second) }.asIterable())
    df.print()
    df.rowwise().print()
```

This fails with IllegalArgumentException.