我遵循官方教程训练的决策树模型。如何从训练模型中提取分割点？

// model
val dt = new DecisionTreeClassifier()
  .setLabelCol("indexedLabel")
  .setFeaturesCol("indexedFeatures")
  .setMaxBins(10)

// Train model.  This also runs the indexers.
val dtm = dt.fit(trainingData)

// extract bin split points
how to do it                   <- ?