public static List sort(GraphDefiner definer) 
{
        List< V > values = definer.getValues();
        Map< R, Vertex< R > > vertices = new HashMap< R, Vertex< R > >();
        // Creating a vertex for each representation
        for (V v : values) {
            R rep = definer.getRepresentation(v);
            vertices.put(rep, new Vertex< R >(rep));
        }
        // Connecting neighbourhooding vertices
        for (V v : values) {
            for (V vn : definer.getNeighbours(v)) {
                vertices.get(definer.getRepresentation(v)).addNeighbour(vertices.get(definer.getRepresentation(vn)));
            }
        }
        // Sorting the representations
        List< R > sortedReps = new TopologicalSort< R >().sort(vertices.values());
        // Transforming the sorted representations to sorted values 
        List< V > sortedValues = new ArrayList< V >(sortedReps.size());
        for (R rep : sortedReps) {
            sortedValues.add(definer.getValue(rep));
        }
        return sortedValues;
}

Sorts a graph topologically.