def add_chain(self, name, wrap=True):
        if wrap:
            self.chains.add(name)
        else:
            self.unwrapped_chains.add(name)
        self.dirty = True
calculate standard deviation and confidence interval for prediction
dataset/ETHPy150Open openstack/nova/nova/network/linux_net.py/IptablesTable.add_chain--crossover with--dataset/ETHPy150Open statsmodels/statsmodels/statsmodels/sandbox/regression/predstd.py/wls_prediction_std