code: def test_predict_is_nonconstant():
      model = pf.GARCH(data=data, p=2, q=2)
      x = model.fit()
      predictions = model.predict_is(h=5, intervals=False)
      assert not np.all(predictions.values == predictions.values[0])
  
imports: import numpy
  import pyflux
  import pandas
  from pandas.io.data import DataReader
  from datetime import datetime
label_desc: Use image node_id 13 for calling a global function with example usage: test_predict_is_nonconstant() without return types