public static Set<AttributedVertex> flatten(Collection<AttributedVertex> vertices) {
		Set<AttributedVertex> set = new HashSet<>();
		for (AttributedVertex vertex : vertices) {
			if (vertex instanceof GroupVertex) {
				set.addAll(((GroupVertex) vertex).children);
			}
			else {
				set.add(vertex);
			}
		}
		return set;
	}
Returns a set of vertices such that all non-group nodes in the given vertices are included
and any group nodes in the given vertices are replaced with their contained vertices.

@param vertices the collection of vertices to flatten into a set of non-group vertices.
@return a set of non-group vertices derived from the given collection where all the group
vertices have been replace with their contained vertices.
Ghidra/Features/GraphServices/src/main/java/ghidra/graph/visualization/GroupVertex.java