code: def test_add_constant_has_constant1d(self):
      x = np.ones(5)
      x = tools.add_constant(x, has_constant="skip")
      assert_equal(x, np.ones((5, 1)))
  
      with pytest.raises(ValueError):
          tools.add_constant(x, has_constant="raise")
  
      assert_equal(
          tools.add_constant(x, has_constant="add"), np.ones((5, 2))
      )
  
imports: from statsmodels.compat.pandas import assert_frame_equal, assert_series_equal
  from statsmodels.compat.python import lrange
  import string
  import numpy
  from numpy.random import standard_normal
  from numpy.testing import assert_almost_equal, assert_array_equal, assert_equal, assert_string_equal
  import pandas
  import pytest
  from statsmodels.datasets import longley
  from statsmodels.tools import tools
  from statsmodels.tools.tools import pinv_extended
label_desc: Use image node_id 3 for calling the TestTools obj's underlying member method code with example usage: obj.test_add_constant_has_constant1d() without return types