public Vertex[] verticesUnreachableFromSources() {
		Set<Vertex> reachable = this.getDescendants(this.getSources());
		Set<Vertex> unreachable = vertices.toSet();
		unreachable.removeAll(reachable);
		return unreachable.toArray(new Vertex[unreachable.size()]);
	}
Returns array of all vertices unreachable from a source. These are the
  vertices descending only from a non-trivial strongly connected component.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/DirectedGraph.java