code: def test_isstationary(self):
      process1 = ArmaProcess.from_coeffs([1.1])
      assert_equal(process1.isstationary, False)
  
      process1 = ArmaProcess.from_coeffs([1.8, -0.9])
      assert_equal(process1.isstationary, True)
  
      process1 = ArmaProcess.from_coeffs([1.5, -0.5])
      print(np.abs(process1.arroots))
      assert_equal(process1.isstationary, False)
  
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 8 for calling the TestArmaProcess obj's underlying member method code with example usage: obj.test_isstationary() without return types