Minor Description
The following code worked for Spark 1.5 but fails for 1.6 (using the WritableStage, UnWritableStage classes in PipelineSuite):
val stages0 = Array(new UnWritableStage("b")) val stages1 = Array(new WritableStage("a")) val steps = stages0 ++ stages1 val p = new Pipeline().setStages(steps) p.stages.w(steps) new ParamPair(p.stages, steps)
This also occurs with a mix of transformers from ml.feature. It is because Java Arrays are non-covariant and the addition of MLWritable to some transformers means the stages0/1 arrays above are not of type Array[PipelineStage].
