code: def test_invalid_func():
      msg = (
          "Provide a custom function lambda x,y: ... "
          'or a string in ("x_mean != y_mean", '
          '"x_mean > y_mean", "x_mean < y_mean")'
      )
      assert_raises(
          AttributeError,
          msg,
          permutation_test,
          [1, 2, 3],
          [3, 4, 5],
          "myfunc",
      )
  
file_path: mlxtend/mlxtend/evaluate/tests/test_permutation.py
imports: import numpy
  from mlxtend.evaluate import permutation_test
  from mlxtend.utils import assert_raises
label_desc: Use image node_id 7 for calling a global function with example usage: test_invalid_func() without return types