code: def test_iterations():
      endog = lake.copy()
      exog = np.c_[
          np.ones_like(endog), np.arange(1, len(endog) + 1) * 1.0
      ]
  
      # Test for n_iter usage
      _, res = gls(endog, exog, order=(1, 0, 0), n_iter=1)
      assert_equal(res.iterations, 1)
      assert_equal(res.converged, None)
  
file_path: statsmodels/statsmodels/tsa/arima/estimators/tests/test_gls.py
imports: import numpy
  import pytest
  from numpy.testing import assert_, assert_allclose, assert_equal, assert_warns, assert_raises
  from statsmodels.tsa.arima.datasets.brockwell_davis_2002 import lake, oshorts
  from statsmodels.tsa.arima.estimators.gls import gls
label_desc: Use image node_id 6 for calling a global function with example usage: test_iterations() without return types