def METHOD_NAME(self, relative_to=None):
    """Retrieves current maintenancen tasks
    Those are tasks whose time window matches the current time and that are
    not cancelled
    """
    now = relative_to or datetime.now()
    return (
        self.get_queryset()
        .exclude(state=MaintenanceTask.STATE_CANCELED)
        .filter(start_time__lte=now, end_time__gte=now)
    )