pub fn starts_from_package(&self, package_id: &PackageId) -> Result<bool, Error> {
        let package_ix = self.graph.package_graph.package_ix(package_id)?;
        Ok(self.starts_from_package_ix(package_ix))
    }
Returns true if the query starts from the given package.

Returns an error if the package ID is unknown.
guppy/src/graph/feature/query.rs