pub fn contains<'a>(&self, feature_id: impl Into<FeatureId<'a>>) -> Result<bool, Error> {
        Ok(self
            .core
            .contains(self.graph.feature_ix(feature_id.into())?))
    }
Returns true if this set contains the given feature ID.

Returns an error if this feature ID was unknown.
guppy/src/graph/feature/resolve.rs