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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 set_lan_port(self, port_id, mac=None):
 """Set LAN port information to configuration. :param port_id: Physical port ID. :param mac: virtual MAC address if virtualization is necessary. """

        port_handler = _parse_physical_port_id(port_id)
        port = self._find_port(port_handler)
        if port:
            port_handler.set_lan_port(port, mac)
        else:
            self._add_port(port_handler, port_handler.create_lan_port(mac))