pub fn from(&self) -> FeatureMetadata<'g> {
        FeatureMetadata {
            graph: DebugIgnore(self.graph.0),
            node: self.graph.dep_graph()[self.from.feature_ix],
            inner: self.from,
        }
    }
Returns the feature which depends on the `to` feature.
guppy/src/graph/feature/graph_impl.rs