code: def test_add_trend_duplicate_name():
      x = pd.DataFrame(np.zeros((10, 1)), columns=["trend"])
      with pytest.warns(ColumnNameConflict):
          add_trend(x, trend="ct")
          y = add_trend(x, trend="ct")
  
      assert "const" in y.columns
      assert "trend_0" in y.columns
  
imports: import numpy
  from numpy.random import RandomState
  from numpy.testing import assert_array_almost_equal, assert_array_equal, assert_equal
  import pandas
  from pandas.testing import assert_frame_equal
  import pytest
  from arch.utility.timeseries import ColumnNameConflict, add_trend
label_desc: Use image node_id 6 for calling a global function with example usage: test_add_trend_duplicate_name() without return types