import time
import functools
from typing import Callable, TypeVar

T = TypeVar("T")

def retry(max_attempts: int = 3, backoff_factor: float = 0.5):
    def decorator(func: Callable[..., T]) -> Callable[..., T]:
        @functools.wraps(func)
        def wrapper(*args, **kwargs) -> T:
            for attempt in range(max_attempts):
                try:
                    return func(*args, **kwargs)
                except Exception:
                    if attempt == max_attempts - 1:
                        raise
                    time.sleep(backoff_factor * (2 ** attempt))
            raise RuntimeError("Unreachable")
        return wrapper
    return decorator

@retry(max_attempts=3)
def fetch_api():
    ...