<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def purge_old_user_tasks():
 """ Delete any UserTaskStatus and UserTaskArtifact records older than ``settings.USER_TASKS_MAX_AGE``. Intended to be run as a scheduled task. """

    limit = now() - settings.USER_TASKS_MAX_AGE
    # UserTaskArtifacts will also be removed via deletion cascading
    UserTaskStatus.objects.filter(created__lt=limit).delete()