code: def test_equi():
      # Test the structure of the equivariant knockoff construction.
  
      np.random.seed(2342)
      exog = np.random.normal(size=(10, 4))
  
      exog1, exog2, sl = _design_knockoff_equi(exog)
  
      exoga = np.concatenate((exog1, exog2), axis=1)
  
      gmat = np.dot(exoga.T, exoga)
  
      cm1 = gmat[0:4, 0:4]
      cm2 = gmat[4:, 4:]
      cm3 = gmat[0:4, 4:]
  
      assert_allclose(cm1, cm2, rtol=1e-4, atol=1e-4)
      assert_allclose(
          cm1 - cm3, np.diag(sl * np.ones(4)), rtol=1e-4, atol=1e-4
      )
  
file_path: statsmodels/statsmodels/stats/tests/test_knockoff.py
imports: import numpy
  from numpy.testing import assert_allclose, assert_array_equal, assert_equal
  import pytest
  import statsmodels.api
  from statsmodels.stats import knockoff_regeffects
  from statsmodels.stats._knockoff import RegressionFDR, _design_knockoff_equi, _design_knockoff_sdp
label_desc: Use image node_id 1 for calling a global function with example usage: test_equi() without return types