code: def test_nominal_reg_splitter():
      dataset = synth.Mv(seed=42).take(200)
      model = tree.HoeffdingTreeRegressor(
          grace_period=10, leaf_prediction="mean"
      )
  
      for x, y in dataset:
          model.learn_one(x, y)
  
      assert model.height > 0
  
      # Evaluates nominal binary splits
      dataset = synth.Mv(seed=42).take(200)
      model = tree.HoeffdingTreeRegressor(
          grace_period=10, leaf_prediction="mean", binary_split=True
      )
  
      for x, y in dataset:
          model.learn_one(x, y)
  
      assert model.height > 0
  
file_path: river/river/tree/test_splitter.py
imports: from __future__ import annotations
  import pytest
  from river import datasets, tree
  from river.datasets import synth
label_desc: Use image node_id 4 for calling a global function with example usage: test_nominal_reg_splitter() without return types