private Set<AttributedVertex> getSourceVerticesFromSelected() {
		Set<AttributedVertex> selectedVertices = getSelectedVertices();
		Set<AttributedVertex> sources = new HashSet<>(selectedVertices);
		for (AttributedVertex v : selectedVertices) {
			Set<AttributedEdge> edges = graph.incomingEdgesOf(v);
			edges.forEach(e -> sources.add(graph.getEdgeSource(e)));
		}
		return sources;
	}
Ungroup the selected vertices. If the focusedVertex is no longer in the graph, null it. This
will happen if the focusedVertex was the GroupVertex
Ghidra/Features/GraphServices/src/main/java/ghidra/graph/visualization/DefaultGraphDisplay.java