def enable_unstable_feature_callback(
    c: click.Context, p: Union[click.Option, click.Parameter], v: tuple[str, ...]
) -> list[Preview]:
    """Compute the features from an --enable-unstable-feature flag."""
    return [Preview[val] for val in v]
Compute the features from an --enable-unstable-feature flag.
src/black/__init__.py