code: def test_add_indep():
      x1 = np.array([0, 0, 0, 0, 0, 1, 1, 1, 2, 2, 2])
      x2 = np.array([0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1])
      x0 = np.ones(len(x2))
      x = np.column_stack(
          [x0, x1[:, None] * np.arange(3), x2[:, None] * np.arange(2)]
      )
      varnames = (
          ["const"]
          + ["var1_%d" % i for i in np.arange(3)]
          + ["var2_%d" % i for i in np.arange(2)]
      )
      xo, vo = add_indep(x, varnames)
  
      assert_equal(xo, np.column_stack((x0, x1, x2)))
      assert_equal((linalg.svdvals(x) > 1e-12).sum(), 3)
      assert_equal(vo, ["const", "var1_1", "var2_1"])
  
imports: import numpy
  from numpy.testing import assert_equal
  from statsmodels.tools.catadd import add_indep
  from scipy import linalg
label_desc: Use image node_id 1 for calling a global function with example usage: test_add_indep() without return types