code: def test_exceptions_pvals():
      with pytest.raises(ValueError, match="Trend must by one"):
          engle_granger_cv("unknown", 2, 500)
      with pytest.raises(
          ValueError, match="The number of cross-sectional"
      ):
          engle_granger_cv("n", 25, 500)
  
file_path: arch/arch/tests/unitroot/test_engle_granger.py
imports: import numpy
  from numpy.testing import assert_allclose
  import pandas
  import pytest
  from statsmodels.iolib.summary import Summary
  from arch.unitroot._engle_granger import engle_granger_cv, engle_granger_pval
  from arch.unitroot._shared import ResidualCointegrationTestResult, _cross_section
  from arch.unitroot.cointegration import engle_granger
label_desc: Use image node_id 5 for calling a global function with example usage: test_exceptions_pvals() without return types