code: def test_bbvi():
      model = pf.GARCH(data=data, p=1, q=1)
      x = model.fit("BBVI", iterations=100)
      assert len(model.latent_variables.z_list) == 4
      lvs = np.array([i.value for i in model.latent_variables.z_list])
      assert len(lvs[np.isnan(lvs)]) == 0
  
imports: import numpy
  import pyflux
  import pandas
  from pandas.io.data import DataReader
  from datetime import datetime
label_desc: Use image node_id 3 for calling a global function with example usage: test_bbvi() without return types