private static AddressSetView gatherAddresses(Program program, Set<FGVertex> vertices) {
		if (vertices.size() == 0) {
			throw new IllegalArgumentException(
				"Cannot create a group vertex with no grouped vertices");
		}

		AddressSet addresses = new AddressSet();
		for (FGVertex vertex : vertices) {
			addresses.add(vertex.getAddresses());
		}
		return addresses;
	}
We need this in the use case that we do NOT relayout the graph each time we group. These
values allow us to restore the vertices to the place from whence they came (even though 
the locations may be irrelevant).
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/graph/vertex/GroupedFunctionGraphVertex.java