new_contents: # -*- coding: utf-8 -*-
  """Example for wald_test for terms - `wald_anova`
  
  Created on Mon Dec 15 11:19:23 2014
  
  Author: Josef Perktold
  License: BSD-3
  
  """
  
  import numpy as np
  
  from statsmodels.formula.api import ols, glm, poisson
  from statsmodels.discrete.discrete_model import Poisson
  
  import statsmodels.stats.tests.test_anova as ttmod
  
  test = ttmod.TestAnova3()
  test.setupClass()
  
  data = test.data.drop([0,1,2])
  res_ols = ols("np.log(Days+1) ~ C(Duration, Sum)*C(Weight, Sum)", data).fit(use_t=False)
  
  res_glm = glm("np.log(Days+1) ~ C(Duration, Sum)*C(Weight, Sum)",
                          data).fit()
  
  res_poi = Poisson.from_formula("Days ~ C(Weight) * C(Duration)", data).fit(cov_type='HC0')
  res_poi_2 = poisson("Days ~ C(Weight) + C(Duration)", data).fit(cov_type='HC0')
  
  print('\nOLS')
  print(res_ols.wald_anova())
  print('\nGLM')
  print(res_glm.wald_anova(skip_single=False, combine_terms=['Duration', 'Weight']))
  print('\nPoisson 1')
  print(res_poi.wald_anova(skip_single=False, combine_terms=['Duration', 'Weight']))
  print('\nPoisson 2')
  print(res_poi_2.wald_anova(skip_single=False))
  
subject: add example for wald_anova