code: def test_poisson_ppc():
      """
      Tests PPC value
      """
      model = pf.GAS(data=countdata, ar=1, sc=1, family=pf.Poisson())
      x = model.fit("BBVI", iterations=200)
      p_value = model.ppc()
      assert 0.0 <= p_value <= 1.0
  
imports: import numpy
  import pyflux
label_desc: Use image node_id 23 for calling a global function with example usage: test_poisson_ppc() without return types