models.py

    comment = models.CharField(
        verbose_name=_("Comment"), blank=True, null=True, max_length=255
    )

    def __str__(self):
        return f"{self.week}, {self.period}, {self.subject}"

    class Meta:
        verbose_name = _("Extra lesson")
        verbose_name_plural = _("Extra lessons")


class ChronosGlobalPermissions(ExtensibleModel):
    class Meta:
        managed = False
        permissions = (
            ("view_all_timetables", _("Can view all timetables")),
            ("view_timetable_overview", _("Can view timetable overview")),
            ("view_lessons_day", _("Can view all lessons per day")),
        )