code: def test_number_public_functions():
      """Check that number of public functions is stable.
  
      If it changes, it means that we have added or removed a public function.
      If this is intentional, then the number should be updated in the test.
      Otherwise it means that the public API of nilearn has changed by mistake.
      """
      assert len({_[0] for _ in all_functions()}) == 240
  
imports: import numpy
  import pytest
  from nilearn._utils import all_classes, all_functions, all_modules
label_desc: Use image node_id 3 for calling a global function with example usage: test_number_public_functions() without return types