code: def test_ppc():
      """
      Tests PPC value
      """
      model = pf.GASReg(
          formula="y ~ x1", data=data, family=pf.Poisson()
      )
      x = model.fit("BBVI", iterations=100)
      p_value = model.ppc()
      assert 0.0 <= p_value <= 1.0
  
imports: import numpy
  import pandas
  import pyflux
label_desc: Use image node_id 20 for calling a global function with example usage: test_ppc() without return types