public Set<Vertex> getParents(Vertex v) {
		Set<Vertex> parents = new HashSet<>();
		Edge e = vertices.getFirstIncomingEdge(v);
		while (e != null) {
			parents.add(e.from());
			e = edges.getNextEdgeWithSameTo(e);
		}
		return parents;
	}
Returns a Set containg all of the vertices from which an edge comes
 into the given vertex.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/DirectedGraph.java