public Set<FGEdge> createDummySinks() {

		Set<FGEdge> dummyEdges = new HashSet<>();
		Set<FGVertex> exits = getExitPoints();
		for (FGVertex exit : exits) {
			AbstractFunctionGraphVertex abstractVertex = (AbstractFunctionGraphVertex) exit;
			FGController controller = abstractVertex.getController();
			ListingFunctionGraphVertex newExit = new ListingFunctionGraphVertex(controller,
				abstractVertex.getAddresses(), RefType.UNCONDITIONAL_JUMP, true);
			newExit.setVertexType(FGVertexType.EXIT);
			FGVertex groupVertex = getVertexForAddress(exit.getVertexAddress());
			FGEdgeImpl edge =
				new FGEdgeImpl(groupVertex, newExit, RefType.UNCONDITIONAL_JUMP, options);
			dummyEdges.add(edge);
		}

		return dummyEdges;
	}
A method to create dummy edges (with dummy vertices).  This is used to add entry and 
exit vertices as needed when a user grouping operation has consumed the entries or exits.
The returned edge will connect the current vertex containing the exit to a new dummy 
vertex that is a sink for the graph.   Calling this method does not mutate this graph.

@return the edge
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/graph/FunctionGraph.java