Edge getLastIncomingEdge(Vertex v) {
		//return lastIncomingEdge[ index( v ) ];
		try {
			Edge re = firstIncomingEdge[keyIndices.get(v.key())];
			Edge e = re;
			EdgeSet es = parentGraph.edges();
			while (e != null) {
				re = e;
				e = es.getNextEdgeWithSameTo(re);
			}
			return re;
		}
		catch (NoValueException exc) {
			return null;
		}
	}
Get the last incoming edge in the internal structures for this 
VertexSet for the parent DirectedGraph.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/VertexSet.java