code: def test_couple_terms_integ():
      """
      Tests the length of the latent variable vector for an ARIMAX model
      with 1 AR and 1 MA term and integrated once, and tests that the
      values are not nan
      """
      model = ARIMAX(
          formula="y ~ x1",
          data=data,
          ar=1,
          ma=1,
          integ=1,
          family=Skewt(),
      )
      x = model.fit()
      assert len(model.latent_variables.z_list) == 7
      lvs = np.array([i.value for i in model.latent_variables.z_list])
      assert len(lvs[np.isnan(lvs)]) == 0
  
imports: import numpy
  import pandas
  from pyflux.arma import ARIMAX
  from pyflux.families import Skewt
label_desc: Use image node_id 3 for calling a global function with example usage: test_couple_terms_integ() without return types