code: def test_waterfall_legacy(explainer):
      """Test the old waterfall plot."""
      shap_values = explainer.shap_values(explainer.data)
      fig = plt.figure()
      shap.plots._waterfall.waterfall_legacy(
          explainer.expected_value, shap_values[0]
      )
      plt.tight_layout()
      return fig
  
file_path: shap/tests/plots/test_waterfall.py
imports: import matplotlib.pyplot
  import numpy
  import pandas
  import pytest
  from sklearn.tree import DecisionTreeRegressor
  import shap
label_desc: Use image node_id 4 for calling a global function with example usage: test_waterfall_legacy(explainer) and returns: fig