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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 _on_import_config(self, *args):
 """Callback method the the import button was clicked Shows a dialog allowing to import an existing configuration file """

        def handle_import(dialog_text, path_name):
            chooser = Gtk.FileChooserDialog(dialog_text, None,
                                            Gtk.FileChooserAction.SAVE,
                                            (Gtk.STOCK_CANCEL, Gtk.ResponseType.CANCEL,
                                             Gtk.STOCK_OPEN, Gtk.ResponseType.ACCEPT))
            chooser.set_current_folder(path_name)
            response = chooser.run()
            if response == Gtk.ResponseType.ACCEPT:
                # get_filename() returns the whole file path inclusively the filename
                config_file = chooser.get_filename()
                config_path = dirname(config_file)
                self._last_path = config_path
                config_dict = yaml_configuration.config.load_dict_from_yaml(config_file)
                config_type = config_dict.get("TYPE")
                if config_type == "SM_CONFIG":
                    del config_dict["TYPE"]
                    self.core_config_model.update_config(config_dict, config_file)
                    logger.info("Imported Core Config from {0}".format(config_file))
                elif config_type == "GUI_CONFIG":
                    del config_dict["TYPE"]
                    self.gui_config_model.update_config(config_dict, config_file)
                    logger.info("Imported GUI Config from {0}".format(config_file))
                else:
                    logger.error("{0} is not a valid config file".format(config_file))
            elif response == Gtk.ResponseType.CANCEL:
                logger.info("Import of configuration cancelled")
            chooser.destroy()

        handle_import("Import Config Config from", self._last_path)

        self.check_for_preliminary_config()
        self.update_path_labels()