code: def get_global_achievement_percentages_for_app(self, gameID, format=None):
          
          parameters = {'gameid' : gameID}
          if format is not None:
              parameters['format'] = format
          url = self.create_request_url(self.interface,
              'GetGlobalAchievementPercentagesForApp', 2, parameters)
          data = self.retrieve_request(url)
          return self.return_data(data, format=format)
docs: Request statistics showing global achievements that have been
          unlocked.
  
          gameID: The id of the game.
          format: Return format. None defaults to json. (json, xml, vdf)