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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 xy_addr0(self):
 """ Assign indicies and variable names for variables used in power flow For each loaded model with the ``pflow`` flag as ``True``, the following functions are called sequentially: * ``_addr()`` * ``_intf_network()`` * ``_intf_ctrl()`` After resizing the ``varname`` instance, variable names from models are stored by calling ``_varname()`` Returns ------- None """

        for device, pflow in zip(self.devman.devices, self.call.pflow):
            if pflow:
                self.__dict__[device]._addr()
                self.__dict__[device]._intf_network()
                self.__dict__[device]._intf_ctrl()

        self.varname.resize()

        for device, pflow in zip(self.devman.devices, self.call.pflow):
            if pflow:
                self.__dict__[device]._varname()