public ProgramSelection getProgramSelectionForAllVertices() {
		AddressSet addresses = new AddressSet();
		for (FGVertex vertex : getVertices()) {
			ProgramSelection programSelection = vertex.getProgramSelection();
			if (programSelection == null) {
				continue;
			}
			addresses.add(programSelection);
		}

		return new ProgramSelection(addresses);
	}
Any time a vertex is grouped we want to make sure that any previous group affiliations
are removed.

@param groupVertices the new grouping of vertices
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/graph/FunctionGraph.java