code: def test_y_none_entropy():
      """Test that an error is raised when y is None and 'entropy' is used."""
      msg_error = "y cannot be None if strategy='entropy'."
      mcb = MultipleCoefficientBinning(n_bins=2, strategy="entropy")
      with pytest.raises(ValueError, match=msg_error):
          mcb.fit(X, None)
  
file_path: pyts/pyts/approximation/tests/test_mcb.py
imports: import numpy
  import pytest
  import re
  from pyts.approximation.mcb import _uniform_bins, _digitize
  from pyts.approximation import MultipleCoefficientBinning
label_desc: Use image node_id 7 for calling a global function with example usage: test_y_none_entropy() without return types