from dataclasses import dataclass, field
from typing import Optional

@dataclass
class Customer:
    id: int
    name: str
    email: str
    address: str
    order_count: int
    is_premium: Optional[bool] = field(default=None)

    def __post_init__(self):
        if self.is_premium is None:
            self.is_premium = self.order_count > 10