public Set<FGVertex> getEntryPoints() {
		HashSet<FGVertex> result = new LinkedHashSet<>();
		for (FGVertex vertex : getVertices()) {
			FGVertexType vertexType = vertex.getVertexType();
			if (vertex.isEntry()) {
				result.add(vertex);
			}
			else if (vertexType == FGVertexType.GROUP) {
				if (groupContainsEntry((GroupedFunctionGraphVertex) vertex)) {
					result.add(vertex);
				}
			}
		}
		return result;
	}
Any time a vertex is grouped we want to make sure that any previous group affiliations
are removed.

@param groupVertices the new grouping of vertices
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/graph/FunctionGraph.java