@abstractmethod
def extract(self, token: str, current_idx: int, relative_idx: int, tokens: Sequence[str], features: Dict[(str, float)]) -> None:
    raise NotImplementedError
@abstractmethod
def extract(self, token: str, current_idx: int, relative_idx: int, tokens: Sequence[str], features: Dict[(str, float)]) -> None:
    raise NotImplementedError