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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _unpack_model(self, om):
 """ Returns data from the OPF model. """

        buses = om.case.connected_buses
        branches = om.case.online_branches
        gens = om.case.online_generators

        cp = om.get_cost_params()

#        Bf = om._Bf
#        Pfinj = om._Pfinj

        return buses, branches, gens, cp