protected GroupedFunctionGraphVertex getGroupVertex(FunctionGraph functionGraph,
			Address address) {
		FGVertex vertex = functionGraph.getVertexForAddress(address);
		if (!(vertex instanceof GroupedFunctionGraphVertex)) {
			if (vertex == null) {
				Msg.debug(this, "Null vertex for address " + address + ".  All vertices: ");
				Collection<FGVertex> vertices = functionGraph.getVertices();
				for (FGVertex v : vertices) {
					Msg.debug(this, "\t" + v);
				}
			}

			Assert.fail("Did not find group vertex at " + address + ".  Instead found " + vertex);
		}
		return (GroupedFunctionGraphVertex) vertex;
	}
Finds an edge that represents the given edge, which may no longer exist with
the same (==) edge instances.
Ghidra/Features/FunctionGraph/src/test.slow/java/ghidra/app/plugin/core/functiongraph/AbstractFunctionGraphTest.java