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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 _intf_network(self):
 """ Retrieve the ac and dc network interface variable indices. :Example: ``self._ac = {'bus1': (a1, v1)}`` gives - indices: self.bus1 - system.Bus.a -> self.a1 - system.Bus.v -> self.v1 ``self._dc = {'node1': v1}`` gives - indices: self.node1 - system.Node.v-> self.v1 :return: None """


        for key, val in self._ac.items():
            self.copy_data_ext(
                model='Bus', field='a', dest=val[0], idx=self.__dict__[key])
            self.copy_data_ext(
                model='Bus', field='v', dest=val[1], idx=self.__dict__[key])

        for key, val in self._dc.items():
            self.copy_data_ext(
                model='Node', field='v', dest=val, idx=self.__dict__[key])

        # check for interface voltage differences
        self._check_Vn()