code: def list_tasks(self, app_id=None, **kwargs):
          
          response = self._do_request(
              'GET', '/v2/apps/%s/tasks' % app_id if app_id else '/v2/tasks')
          tasks = self._parse_response(
              response, MarathonTask, is_list=True, resource_name='tasks')
          [setattr(t, 'app_id', app_id)
           for t in tasks if app_id and t.app_id is None]
          for k, v in kwargs.items():
              tasks = [o for o in tasks if getattr(o, k) == v]
  
          return tasks
docs: List running tasks, optionally filtered by app_id.
  
          :param str app_id: if passed, only show tasks for this application
          :param kwargs: arbitrary search filters
  
          :returns: list of tasks
          :rtype: list[:class:`marathon.models.task.MarathonTask`]