code: def test_entropy():
      """Test entropy function."""
      assert entropy(np.ones((10, 1))) == 0.0
  
file_path: sktime/sktime/annotation/tests/test_igts.py
imports: import numpy
  import pytest
  from sktime.annotation.igts import IGTS, InformationGainSegmentation, entropy
label_desc: Use image node_id 2 for calling a global function with example usage: test_entropy() without return types