code: def test_get_outlier_cols():
      """Check the non-steady state columns are detached."""
      col_names = ["confound_regressor"]
      non_steady_state = [
          f"non_steady_state_outlier{i:02d}" for i in range(3)
      ]
      col_names += non_steady_state
      col_names = pd.Index(col_names)
      outlier_cols, confounds_cols = _get_outlier_cols(col_names)
      assert confounds_cols == ["confound_regressor"]
      assert outlier_cols == non_steady_state
  
file_path: nilearn/nilearn/interfaces/fmriprep/tests/test_load_confounds_scrub.py
imports: import numpy
  import pandas
  import pytest
  from pandas.testing import assert_frame_equal
  from nilearn.interfaces.fmriprep.load_confounds_scrub import _get_outlier_cols, extract_outlier_regressors, optimize_scrub
label_desc: Use image node_id 2 for calling a global function with example usage: test_get_outlier_cols() without return types