docs: def get_user_group_list(self, steamID, format=None):
          """Request a list of groups a user is subscribed to.
  
          steamID: User ID
          format: Return format. None defaults to json. (json, xml, vdf)
  
          """
          parameters = {'steamid' : steamID}
          if format is not None:
              parameters['format'] = format
          url = self.create_request_url(self.interface, 'GetUserGroupList', 1,
              parameters)
          data = self.retrieve_request(url)
          return self.return_data(data, format=format)