class DisplayMixin:
    def json_format(self):
        return {
            "id": self.id,
            "telegram_id": self.telegram_id,
            "username": self.username,
            "lang_code": self.lang_code,
            "meta": self.meta,
            "last_use": self.last_use.isoformat(),
            "created": self.created.isoformat()
        }

    def front_format(self, plain_text=True):
        if not plain_text:
            raise NotImplementedError

        return f"{self.meta.get('first_name') or ''} {self.meta.get('last_name') or ''}".strip()