code: def is_playing_shared_game(self, steamID, appid_playing, format=None):
          
          parameters = {'steamid' : steamID, 'appid_playing' : appid_playing}
          if format is not None:
              parameters['format'] = format
          url = self.create_request_url(self.interface, 'IsPlayingSharedGame', 1,
              parameters)
          data = self.retrieve_request(url)
          return self.return_data(data, format=format)
docs: Returns valid lender SteamID if game currently played is borrowed.
  
          steamID: The users ID
          appid_playing: The game player is currently playing
          format: Return format. None defaults to json. (json, xml, vdf)