@Override
	public void unionWith(DirectedGraph otherGraph) {
		DoubleAttribute<Edge> otherWts =
			(DoubleAttribute<Edge>) otherGraph.edgeAttributes().getAttribute("weight");
		GraphIterator<Vertex> vi = otherGraph.vertexIterator();
		while (vi.hasNext()) {
			add(vi.next());
		}
		GraphIterator<Edge> ei = otherGraph.edgeIterator();
		while (ei.hasNext()) {
			Edge e = ei.next();
			try {
				add(e, otherWts.getValue(e));
			}
			catch (NoValueException e1) {
				add(e);
			}
		}
	}
Creates union of graphs in place by adding all vertices and edges of
other graph to this graph. This method used to return a different graph
as the union but now does not.
Ghidra/Framework/Generic/src/main/java/ghidra/util/graph/WeightedDigraph.java