code: def test_interpolate_trend(self):
      x = np.arange(12)
      freq = 4
      trend = seasonal_decompose(x, period=freq).trend
      assert_equal(trend[0], np.nan)
  
      trend = seasonal_decompose(
          x, period=freq, extrapolate_trend=5
      ).trend
      assert_almost_equal(trend, x)
  
      trend = seasonal_decompose(
          x, period=freq, extrapolate_trend="freq"
      ).trend
      assert_almost_equal(trend, x)
  
      trend = seasonal_decompose(
          x[:, None], period=freq, extrapolate_trend=5
      ).trend
      assert_almost_equal(trend, x)
  
      # 2d case
      x = np.tile(np.arange(12), (2, 1)).T
      trend = seasonal_decompose(
          x, period=freq, extrapolate_trend=1
      ).trend
      assert_almost_equal(trend, x)
  
      trend = seasonal_decompose(
          x, period=freq, extrapolate_trend="freq"
      ).trend
      assert_almost_equal(trend, x)
  
imports: from statsmodels.compat.pandas import MONTH_END, QUARTER_END, YEAR_END
  import numpy
  from numpy.testing import assert_allclose, assert_almost_equal, assert_equal, assert_raises
  import pandas
  import pytest
  from statsmodels.tsa.seasonal import seasonal_decompose
label_desc: Use image node_id 8 for calling the TestDecompose obj's underlying member method code with example usage: obj.test_interpolate_trend() without return types