pub fn query_directed<'g, 'a>(
        &'g self,
        package_ids: impl IntoIterator<Item = &'a PackageId>,
        dep_direction: DependencyDirection,
    ) -> Result<PackageQuery<'g>, Error> {
        match dep_direction {
            DependencyDirection::Forward => self.query_forward(package_ids),
            DependencyDirection::Reverse => self.query_reverse(package_ids),
        }
    }
Creates a new query that returns transitive dependencies of the given packages in the
specified direction.

Returns an error if any package IDs are unknown.
guppy/src/graph/query.rs