Using Dataclasses for Configuration in Python

---receipt:     Oz-Ware Purchase Invoicedate:        2012-08-06customer:    first_name:   Dorothy    family_name:  Galeitems:    - part_no:   A4786      descrip:   Water Bucket (Filled)      price:     1.47      quantity:  4    - part_no:   E1628      descrip:   High Heeled "Ruby" Slippers      size:      8      price:     133.7      quantity:  1bill-to:  &id001    street: |            123 Tornado Alley            Suite 16    city:   East Centerville    state:  KSship-to:  *id001specialDelivery:  >    Follow the Yellow Brick    Road to the Emerald City.    Pay no attention to the    man behind the curtain.

config = {    "reciept": "Oz-Ware Purchase Invoice",    "date": "2012-08-06",    "customer": {        "first_name": "Dorothy",        "family_name": "Gale",    },    "items": [        {            "part_no": "A4786",            "descrip": "Water Bucket (Filled)",            "price": 1.47,            "quantity": 4,        },        {            "part_no": "E1628",            "descrip": "High Heeled \"Ruby\" Slippers",            "size": 8,            "price": 133.7,            "quantity": 1,        },    ],    "bill-to": {        "street" : "123 Tornado Alley
Suite 16",        "city": "East Centerville",        "state": "KS",    },    "ship-to": {        "street" : "123 Tornado Alley
Suite 16",        "city": "East Centerville",        "state": "KS",    },    "specialDelivery": "Follow the Yellow Brick Road to the Emerald City. Pay no attention to the man behind the curtain.",}

import typing as tfrom dataclasses import dataclassfrom datetime import date@dataclassclass Item:    part_no: str    description: str    price: float    quantity: int    size: int = None    def __post_init__(self):        # Do some validation        if self.quantity <= 0:            raise ValueError("quantity must be greater than zero")    @classmethod    def from_dict(cls: t.Type["Item"], obj: dict):        return cls(            part_no=obj["part_no"],            description=obj["descrip"],            price=obj["price"],            quantity=obj["quantity"],            size=obj.get("size"),        )@dataclassclass Customer:    first_name: str    family_name: str    @classmethod    def from_dict(cls: t.Type["Customer"], obj: dict):        return cls(            first_name=obj["first_name"],            last_name=obj["family_name"],        )@dataclassclass Address:    street: str    city: str    state: str    @classmethod    def from_dict(cls: t.Type["Address"], obj: dict):        return cls(            street=obj["street"],            city=obj["city"],            state=obj["state"],        )@dataclassclass Order:    reciept: str    date: date    customer: Customer    items: t.Sequence[Item]    bill_to: Address    ship_to: Address    special_delivery: str = None    @classmethod    def from_dict(cls: t.Type["Order"], obj: dict):        return cls(            receipt=obj["reciept"],            date=date(obj["date"]),            customer=Customer.from_dict(obj["customer"]),            items=[Item.from_dict(item) for item in obj["items"]),            bill_to=Address.from_dict(obj["bill-to"]),            ship_to=Address.from_dict(obj["ship-to"]),            special_delivery=obj.get("specialDelivery"),        )

raw_config = {...}config = Order.from_dict(raw_config)config.customer.first_name

import unittestfrom .config import Orderclass TestOrderConfig(unittest.TestCase):    def test_example_config(self):        raw_config = {...}        expected = Order(            customer=Customer(...),            ...        )        self.assertEqual(Order.from_dict(raw_config), expected)