message: Output leaf index for core interface
diff: @@ -186,6 +186,10 @@ def model_builder(features,
  train_op_fn=_train_op_fn,
  logits=logits)
  + if output_leaf_index and gbdt_batch.LEAF_INDEX in predictions_dict:
  + estimator_spec.predictions[gbdt_batch.LEAF_INDEX] = predictions_dict[
  + gbdt_batch.LEAF_INDEX]
  +
  estimator_spec = estimator_spec._replace(
  training_hooks=training_hooks + list(estimator_spec.training_hooks))
  return estimator_spec
  