class User:
    def __init__(self, username: str):
        self._username = username
        self._authenticated = False

    def is_authenticated(self) -> bool:
        return self._authenticated

    def is_active(self) -> bool:
        return True

    def is_anonymous(self) -> bool:
        return False

    def get_id(self) -> str:
        return self._username

    def validate(self, _: str) -> bool:
        raise NotImplementedError()