def forwards(apps, schema_editor):
    """
    Copy the ClassicalWork and DancePiece data to use the new through models.
    """
    Event = apps.get_model('spectator_events', 'Event')
    ClassicalWorkSelection = apps.get_model(
                                'spectator_events', 'ClassicalWorkSelection')
    DancePieceSelection = apps.get_model(
                                'spectator_events', 'DancePieceSelection')

    for event in Event.objects.all():

        for work in event.classicalworks.all():
            selection = ClassicalWorkSelection(
                            classical_work=work,
                            event=event)
            selection.save()

        for piece in event.dancepieces.all():
            selection = DancePieceSelection(
                            dance_piece=piece,
                            event=event)
            selection.save()
Copy the ClassicalWork and DancePiece data to use the new through models.