code: def test_null_model_small():
      """Test a small null model."""
      explainer = shap.KernelExplainer(
          lambda x: np.zeros(x.shape[0]), np.ones((2, 4)), nsamples=100
      )
      e = explainer.explain(np.ones((1, 4)))
      assert np.sum(np.abs(e)) < 1e-8
  
file_path: shap/tests/explainers/test_kernel.py
imports: import numpy
  import pandas
  import scipy.sparse
  import sklearn
  import shap
label_desc: Use image node_id 1 for calling a global function with example usage: test_null_model_small() without return types