permission_set=models.ForeignKey(PermissionSet,null=True,blank=True,help_text="If set then determines the subset of permissions that are granted by this token, rathen than granting full user permissions.")
expiry=models.DateTimeField(default=None,blank=True,null=True,help_text="If set then determines when the token will no longer be treated as valid. If left empty the token will not expire.")