code: def test_get_node_feature(spark_dtree):
      assert (
          spark_dtree.get_node_feature(0) == 1
      ), "Feature index for node 0 should be 1"
      assert (
          spark_dtree.get_node_feature(1) == 3
      ), "Feature index for node 1 should be 3"
      assert (
          spark_dtree.get_node_feature(3) == -1
      ), "Feature index for node 3 should be -1"
      assert (
          spark_dtree.get_node_feature(7) == 3
      ), "Feature index for node 7 should be 3"
      assert (
          spark_dtree.get_node_feature(8) == 0
      ), "Feature index for node 8 should be 0"
      assert (
          spark_dtree.get_node_feature(12) == 6
      ), "Feature index for node 12 should be 6"
      assert (
          spark_dtree.get_node_feature(16) == -1
      ), "Feature index for node 16 should be -1"
  
imports: import numpy
  import pyspark
  import pytest
  from pyspark.ml.classification import DecisionTreeClassificationModel
  from pyspark.sql import SparkSession
  from dtreeviz.models.spark_decision_tree import ShadowSparkTree
label_desc: Use image node_id 10 for calling a global function with example usage: test_get_node_feature(spark_dtree) without return types