'regress endog on exog without one of the variables
This uses a k_vars loop, only attributes of the OLS instance are stored.
Parameters
attributes : list of strings
These are the names of the attributes of the auxiliary OLS results
instance that are stored and returned.
not yet used'

def _get_drop_vari(self, attributes):

    from statsmodels.sandbox.tools.cross_val import LeaveOneOut
    endog = self.results.model.endog
    exog = self.exog
    cv_iter = LeaveOneOut(self.k_vars)
    res_loo = defaultdict(list)
    for (inidx, outidx) in cv_iter:
        for att in attributes:
            res_i = self.model_class(endog, exog[:, inidx]).fit()
            res_loo[att].append(getattr(res_i, att))
    return res_loo
