'Fits the model and provides regression results.
Returns
Results : class
Empirical likelihood regression class'

def fit(self):

    exog_with = add_constant(self.exog, prepend=True)
    restricted_model = OLS(self.endog, exog_with)
    restricted_fit = restricted_model.fit()
    restricted_el = restricted_fit.el_test(np.array([0]), np.array([0]), ret_params=1)
    params = np.squeeze(restricted_el[3])
    beta_hat_llr = restricted_el[0]
    llf = np.sum(np.log(restricted_el[2]))
    return OriginResults(restricted_model, params, beta_hat_llr, llf)
