code: def test_returns_inputs():
      # see 1960
      y = [0] * 10 + [1] * 10
      x = np.arange(20)
      result = lowess(y, x, frac=0.4)
      assert_almost_equal(result, np.column_stack((x, y)))
  
imports: import os
  import numpy
  from numpy.testing import assert_, assert_allclose, assert_almost_equal, assert_equal, assert_raises
  import pytest
  from statsmodels.nonparametric.smoothers_lowess import lowess
  import pandas
label_desc: Use image node_id 1 for calling a global function with example usage: test_returns_inputs() without return types