public Iterable<FcgVertex> getVerticesByLevel(FcgLevel level) {
		return IterableUtils.unmodifiableIterable(verticesByLevel.get(level));
	}
Returns all vertices in the given level.  The result will be non-null.

@param level the level of the vertices to retrieve
@return all vertices in the given level
Ghidra/Features/GraphFunctionCalls/src/main/java/functioncalls/graph/FunctionCallGraph.java