@Override
	public FunctionCallGraph copy() {

		FunctionCallGraph newGraph = new FunctionCallGraph();
		for (FcgVertex v : vertices.keySet()) {
			newGraph.addVertex(v);
		}

		for (FcgEdge e : edges.keySet()) {
			newGraph.addEdge(e);
		}

		return newGraph;
	}
Returns the largest level (the furthest level from the source node) in the given 
direction 

@param direction the direction to search
@return the largest level
Ghidra/Features/GraphFunctionCalls/src/main/java/functioncalls/graph/FunctionCallGraph.java