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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 _check_Vn(self):
 """Check data consistency of Vn and Vdcn if connected to Bus or Node :return None """

        if hasattr(self, 'bus') and hasattr(self, 'Vn'):
            bus_Vn = self.read_data_ext('Bus', field='Vn', idx=self.bus)
            for name, bus, Vn, Vn0 in zip(self.name, self.bus, self.Vn,
                                          bus_Vn):
                if Vn != Vn0:
                    self.log(
                        '<{}> has Vn={} different from bus <{}> Vn={}.'.format(
                            name, Vn, bus, Vn0), WARNING)

        if hasattr(self, 'node') and hasattr(self, 'Vdcn'):
            node_Vdcn = self.read_data_ext('Node', field='Vdcn', idx=self.node)
            for name, node, Vdcn, Vdcn0 in zip(self.name, self.node, self.Vdcn,
                                               node_Vdcn):
                if Vdcn != Vdcn0:
                    self.log(
                        '<{}> has Vdcn={} different from node <{}> Vdcn={}.'
                        .format(name, Vdcn, node, Vdcn0), WARNING)