def set_rarity(apps, schema_editor):
    ITEM_RARITIES = {
        "Rare": lambda r: r <= 10,
        "Very Rare": lambda r: 11 <= r <= 20,
        "Extremely Rare": lambda r: 21 <= r <= 30,
        "Mega Rare": lambda r: r > 30,
    }

    Item = apps.get_model("main_app", "Item")
    items = Item.objects.all()

    for item in items:
        for rarity, condition in ITEM_RARITIES.items():
            if condition(item.price):
                item.rarity = rarity
                break

    Item.objects.bulk_update(items, ["rarity"])