Function shortest_path_using_outgoing 

pub fn shortest_path_using_outgoing(
    from_id: &str,
    to_id: &str,
    kind: Option<&str>,
    max_hops: Option<usize>,
    outgoing_edges: impl FnMut(&str, Option<&str>) -> Result<Vec<GraphEdge>, Error>,
) -> Result<Option<GraphPath>, Error>