code: def test_init():
      with pytest.raises(ValueError):
          FeatureNames()
      with pytest.raises(ValueError):
          FeatureNames(unkn_template="%d")
      with pytest.raises(ValueError):
          FeatureNames(n_features=10)
      with pytest.raises(ValueError):
          FeatureNames(["a"], n_features=10)
      with pytest.raises(TypeError):
          FeatureNames({"a", "b"})
      with pytest.raises(ValueError):
          FeatureNames({0: "a", 1: "b"}, n_features=10)
      FeatureNames(unkn_template="%d", n_features=10)
      FeatureNames(["a", "b"])
      FeatureNames({0: "a", 1: "b"})
      FeatureNames({0: "a", 1: "b"}, n_features=10, unkn_template="x%d")
  
file_path: eli5/tests/test_feature_names.py
imports: import pytest
  import numpy
  from eli5._feature_names import FeatureNames
label_desc: Use image node_id 3 for calling a global function with example usage: test_init() without return types