private FGVertex checkForGroupVertex(FGController controller, FGVertex vertex,
			Point2D location) {

		if (!(vertex instanceof GroupedFunctionGraphVertex)) {
			return vertex;
		}

		// Make sure this vertex is added to the graph.  We have to do this here, as 
		// this method getVertex() is recursive and we cannot build-up the edges of 
		// lower-level grouped nodes if they have never been added to the graph.
		boolean installed =
			controller.installGroupVertex((GroupedFunctionGraphVertex) vertex, location);
		return installed ? vertex : null;
	}
Locates a vertex for the given info <b>without creating that vertex</b>.  This is in 
contrast to {@link #getVertex(FGController, Map)}, which will create a vertex
(and supporting vertices if it is a group).

@param controller the controller of the current graph
@param vertexMap a mapping of hashed addresses to vertices (creating this upfront is more
       efficient when using it over different {@link GroupedVertexInfo} instances.
@return an existing vertex; null if one does not exist
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/graph/vertex/GroupedVertexInfo.java