code: def test_arma_impulse_response():
      arrep = arma_impulse_response(armarep.ma, armarep.ar, leads=21)[
          1:
      ]
      marep = arma_impulse_response(armarep.ar, armarep.ma, leads=21)[
          1:
      ]
      assert_array_almost_equal(armarep.marep.ravel(), marep, 14)
      # difference in sign convention to matlab for AR term
      assert_array_almost_equal(-armarep.arrep.ravel(), arrep, 14)
  
imports: from statsmodels.compat.pandas import QUARTER_END
  import datetime
  import numpy
  from numpy.testing import assert_, assert_allclose, assert_almost_equal, assert_array_almost_equal, assert_equal, assert_raises
  import pandas
  import pytest
  from statsmodels.sandbox.tsa.fftarma import ArmaFft
  from statsmodels.tsa.arima.model import ARIMA
  from statsmodels.tsa.arima_process import ArmaProcess, arma_acf, arma_acovf, arma_generate_sample, arma_impulse_response, index2lpol, lpol2index, lpol_fiar, lpol_fima
  from statsmodels.tsa.tests.results import results_arma_acf
  from statsmodels.tsa.tests.results.results_process import armarep
label_desc: Use image node_id 9 for calling a global function with example usage: test_arma_impulse_response() without return types