def el_test(self, b0_vals, param_nums, method='nm',
                            stochastic_exog=1, return_weights=0):
        b0_vals = np.hstack((0, b0_vals))
        param_nums = np.hstack((0, param_nums))
        test_res = self.model.fit().el_test(b0_vals, param_nums, method=method,
                                  stochastic_exog=stochastic_exog,
                                  return_weights=return_weights)
        llr_test = test_res[0]
        llr_res = llr_test - self.llr
        pval = chi2.sf(llr_res, self.model.exog.shape[1] - 1)
        if return_weights:
            return llr_res, pval, test_res[2]
        else:
            return llr_res, pval
test reflection of NULL/NOT NULL, in particular with TIMESTAMP
dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/emplike/originregress.py/OriginResults.el_test--crossover with--dataset/ETHPy150Open zzzeek/sqlalchemy/test/dialect/mysql/test_reflection.py/ReflectionTest.test_nullable_reflection