reduceGroupsK
inline fun <KEY, VALUE> KeyValueGroupedDataset<KEY, VALUE>.reduceGroupsK( noinline func: (VALUE, VALUE) -> VALUE): Dataset<Tuple2<KEY, VALUE>>
(Kotlin-specific) Reduces the elements of each group of data using the specified binary function. The given function must be commutative and associative or the result may be non-deterministic.
Note that you need to use reduceGroupsK always instead of the Java- or Scala-specific KeyValueGroupedDataset.reduceGroups to make the compiler work.