code: def test_bind_df_model():
      class ModelFit(object):
          k_exog = 2
          k_trend = 1
          k_ar = 3
          k_ma = 2
          k_seasonal_ar = 1
          k_seasonal_ma = 2
  
      class ARIMAResults(object):
          pass
  
      fit = ModelFit()
      res = ARIMAResults()
  
      # First, there is no 'df_model' in arima res
      assert not hasattr(res, "df_model")
      bind_df_model(fit, res)
  
      # Now it should
      assert hasattr(res, "df_model")
      assert res.df_model == 11, res.df_model
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_bind_df_model() without return types