Unpersist return type

[German Schiavon]

Hello!

I'd like to ask if there is any reason to return *type *when calling
*dataframe.unpersist*

def unpersist(blocking: Boolean): this.type = {
  sparkSession.sharedState.cacheManager.uncacheQuery(
    sparkSession, logicalPlan, cascade = false, blocking)
  this
}


Just pointing it out because this example from the docs don't compile since
unpersist() is not Unit

streamingDF.writeStream.foreachBatch { (batchDF: DataFrame, batchId: Long) =>
  batchDF.persist()
  batchDF.write.format(...).save(...)  // location 1
  batchDF.write.format(...).save(...)  // location 2
  batchDF.unpersist()}


Thanks!