@Override
	public void dispose() {

		//
		// Let's go a bit overboard and help the garbage collector cleanup by nulling out
		// references and removing the data from Jung's graph
		//
		for (FGVertex vertex : getVertices()) {
			vertex.dispose();
		}

		vertices.clear();
		edges.clear();

		ungroupedEdges.clear();
		groupHistorySet.clear();
		ungroupedEdges = null;
		groupHistorySet = null;
		focusedVertex = null;
		rootVertex = null;
		settings = null;

		graphLayout.dispose();

		graphLayout = null;

		super.dispose();
	}
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