public static <V, E extends GEdge<V>> Set<V> getAncestors(GDirectedGraph<V, E> g,
			Collection<V> vertices) {

		Set<E> edges = getEdgesFrom(g, vertices, false);
		Set<V> ancestors = toVertices(edges);
		return ancestors;
	}
Returns all ancestors for the given vertices in the given graph.  Ancestors for a given
vertex are all nodes at the incoming side of an edge, as well as their incoming 
vertices, etc.

@param g the graph
@param vertices the vertices for which to find descendants
@return the ancestors
Ghidra/Framework/Graph/src/main/java/ghidra/graph/GraphAlgorithms.java