validation of business invariants for payment creation

payment.py

from __future__ import annotations
from typing import List

from src.domain.models.domain_event import DomainEvent
from src.domain.models.payment_created import PaymentCreated

class Payment:
    def __init__(self, payment_id: str):
        self._payment_id = payment_id
        self._events = []

    @classmethod
    def create(cls, payment_id: str, amount_due: float) -> Payment:
        # validation of business invariant
        if amount_due <= 0:
          raise Exception('Amount due should be positive')
          
        payment = cls(payment_id)
        payment.record_that(PaymentCreated(payment_id, amount_due))
        return payment

    def apply_payment_created(self, event: PaymentCreated):
        self._status = 'PENDING_PROCESSING'
        self._amount_due = event.amount_due

    # the existing implementation