def METHOD_NAME(self, ph):
    dual_resid = {}
    for s in ph.local_scenarios.values():
        for ndn_i in s._mpisppy_data.nonant_indices:
            dual_resid[ndn_i] = s._mpisppy_model.rho[ndn_i].value * \
                    math.fabs( s._mpisppy_model.xbars[ndn_i].value - self._prev_avg[ndn_i] )
    return dual_resid