public int inValence(Vertex v) {
		int inv = 0;
		Edge e = vertices.getFirstIncomingEdge(v);
		while (e != null) {
			inv++;
			e = edges.getNextEdgeWithSameTo(e);
		}
		return inv;
	}
The number of edges having v as their terminal or
 "to" vertex.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/DirectedGraph.java