import json
from typing import TypeVar, Type


T = TypeVar('T', bound='TrainDto')

class TrainDto:
    def __init__(self, is_spam: bool, text: str):
        self.is_spam = is_spam
        self.text = text

    def to_json(self) -> str:
        return json.dumps({
            'is_spam': self.is_spam,
            'text': self.text
        })

    @classmethod
    def from_json(cls: Type[T], s: str) -> T:
        j = json.loads(s)
        if not 'is_spam' in j or not 'text' in j:
            raise Exception("Wrong format")
        return TrainDto(is_spam=j['is_spam'], text=j['text'])