def show_help(self, showitem = None):
        """ show_help
            Without any input this funtion shows general common help message.
            When the showitem is given, the corresponding help message will be
            displayed, if exists.
        """
        if showitem is None:
            print(self._general_help)
        else:
            try:
                print(self._specific_help[showitem])
            except KeyError:
                print('No help on %s available'%showitem)
 show_help
            Without any input this funtion shows general common help message.
            When the showitem is given, the corresponding help message will be
            displayed, if exists.
        
recipes/Python/577860_HelpMaker_builds_help_message_comments/recipe-577860.py