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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 prepare_destruction(self):
 """Saves current configuration of windows and panes to the runtime config file, before RAFCON is closed."""

        plugins.run_hook("pre_destruction")

        logger.debug("Saving runtime config to {0}".format(global_runtime_config.config_file_path))

        # store pane last positions
        for key, widget_name in constants.PANE_ID.items():
            global_runtime_config.store_widget_properties(self.view[widget_name], key.replace('_POS', ''))

        # store hidden or undocked widget flags correctly -> make them independent for restoring
        for window_key in constants.UNDOCKABLE_WINDOW_KEYS:
            hidden = False
            if not global_runtime_config.get_config_value(window_key + "_WINDOW_UNDOCKED"):
                hidden = getattr(self, window_key.lower() + '_hidden')
            global_runtime_config.set_config_value(window_key + '_HIDDEN', hidden)

        global_runtime_config.save_configuration()
        
        # state-editor will relieve it's model => it won't observe the state machine manager any more
        self.get_controller('states_editor_ctrl').prepare_destruction()  # avoid new state editor TODO tbd (deleted)
        rafcon.core.singleton.state_machine_manager.delete_all_state_machines()
        rafcon.core.singleton.library_manager.prepare_destruction()

        # gtkmvc installs a global glade custom handler that holds a reference to the last created View class,
        # preventing it from being destructed. By installing a dummy callback handler, after all views have been
        # created, the old handler is being removed and with it the reference, allowing all Views to be destructed.

        # Gtk TODO: check if necessary and search for replacement
        # try:
        #     from gtk import glade
        #     def dummy(*args, **kwargs):
        #         pass
        #     glade.set_custom_handler(dummy)
        # except ImportError:
        #     pass

        # Recursively destroys the main window
        self.destroy()
        from rafcon.gui.clipboard import global_clipboard
        global_clipboard.destroy()
        gui_singletons.main_window_controller = None