code: def test_OLS(X, Y):
      model = OLSModel(design=X)
      results = model.fit(Y)
      assert results.df_residuals == 30
      assert results.residuals.shape[0] == 40
      assert results.predicted.shape[0] == 40
  
file_path: nilearn/nilearn/glm/tests/test_regression.py
imports: import pytest
  from numpy.testing import assert_almost_equal, assert_array_almost_equal, assert_array_equal
  from nilearn.glm import ARModel, OLSModel, SimpleRegressionResults
label_desc: Use image node_id 3 for calling a global function with example usage: test_OLS(X, Y) without return types