Function compute_scc 

pub fn compute_scc<N, E>(graph: &Graph<N, E>) -> SccResult
where
    N: ClassNode,
    E: EdgeKind,

Compute SCCs and the condensation DAG for graph.

Generic over N: ClassNode and E: EdgeKind so this works on both OwnedGraph (from GraphML) and kg-store graph types that implement those traits.