code: def test_integrated_process(ar_params, diff, ma_params, sigma2):
      # Test loglikelihood computation when model has integration
  
      nobs = 100
  
      endog = np.cumsum(np.random.normal(size=nobs))
  
      # Innovations algorithm approach
      llf_obs = arma_innovations.arma_loglikeobs(
          np.diff(endog, diff), ar_params, ma_params, sigma2
      )
  
      # Kalman filter apparoach
      mod = SARIMAX(
          endog,
          order=(len(ar_params), diff, len(ma_params)),
          simple_differencing=True,
      )
      res = mod.filter(np.r_[ar_params, ma_params, sigma2])
  
      # Test that the two approaches are identical
      assert_allclose(llf_obs, res.llf_obs)
  
file_path: statsmodels/statsmodels/tsa/innovations/tests/test_cython_arma_innovations_fast.py
imports: import numpy
  import pytest
  from numpy.testing import assert_equal, assert_allclose
  from statsmodels.tsa.arima_process import arma_acovf
  from statsmodels.tsa.innovations import _arma_innovations, arma_innovations
  from statsmodels.tsa.statespace.sarimax import SARIMAX
label_desc: Use image node_id 5 for calling a global function with example usage: test_integrated_process(ar_params, diff, ma_params, sigma2) without return types