@validate_schema(required_keys={"order_id", "customer_id", "amount", "status"})
def normalize_order(order: dict) -> dict:
    return {
        "order_id": order["order_id"],
        "customer_id": order["customer_id"],
        "amount": round(float(order["amount"]), 2),
        "status": order["status"].lower().strip(),
        "note": order.get("note", ""),   # optional — fine to be absent
    }


# Valid record — passes through
normalize_order({"order_id": 1, "customer_id": 101, "amount": "59.99", "status": "Completed"})
# {"order_id": 1, "customer_id": 101, "amount": 59.99, "status": "completed", "note": ""}

# Missing amount — caught immediately
normalize_order({"order_id": 2, "customer_id": 102, "status": "Completed"})
# ValueError: Missing required keys: {'amount'}

# Wrong type entirely — also caught
normalize_order([1, 101, 59.99, "completed"])
# TypeError: Expected dict, got list