code: def _update_cache(self, course, taskid):
          
          if not id_checker(taskid):
              raise InvalidNameException("Task with invalid name: " + taskid)
  
          task_fs = self.get_task_fs(course.get_id(), taskid)
          last_modif, translation_fs, task_content = self._get_last_updates(course, taskid, task_fs, True)
  
          self._cache[(course.get_id(), taskid)] = (
              self._task_class(course, taskid, task_content, task_fs, translation_fs, self._hook_manager, self._task_problem_types),
              last_modif
          )
docs: Updates the cache
          :param course: a Course object
          :param taskid: a (valid) task id
          :raise InvalidNameException, TaskNotFoundException, TaskUnreadableException