pub fn to_package_set(&self) -> PackageSet<'g> {
        let included: IxBitSet = self
            .core
            .included
            .ones()
            .map(|feature_ix| {
                self.graph
                    .package_ix_for_feature_ix(NodeIndex::new(feature_ix))
            })
            .collect();
        PackageSet::from_included(self.graph.package_graph, included.0)
    }
Converts this `FeatureSet` into a `PackageSet` containing all packages with any selected
features (including the "base" feature).
guppy/src/graph/feature/resolve.rs