pub fn member_by_path(&self, path: impl AsRef<Utf8Path>) -> Result<PackageMetadata<'g>, Error> {
        let path = path.as_ref();
        let id = self
            .inner
            .members_by_path
            .get(path)
            .ok_or_else(|| Error::UnknownWorkspacePath(path.to_path_buf()))?;
        Ok(self.graph.metadata(id).expect("valid package ID"))
    }
Maps the given path to the corresponding workspace member.

Returns an error if the path didn't match any workspace members.
guppy/src/graph/graph_impl.rs