show_all_files option is disabled: hide all root items except *item*
        show_all_files option is enabled: do nothing

def __hide_or_show_root_items(self, item):
        """
        show_all_files option is disabled: hide all root items except *item*
        show_all_files option is enabled: do nothing
        """
        for _it in self.get_top_level_items():
            _it.setHidden(_it is not item and not self.show_all_files)