public static <V, E extends GEdge<V>> List<V> preOrder(GDirectedGraph<V, E> g) {
		return preOrder(g, GraphNavigator.topDownNavigator());
	}
Returns the vertices of the given graph in pre-order, which is the order the vertices
are encountered when performing a depth-first traversal.

@param g the graph
@return the vertices in pre-order
Ghidra/Framework/Graph/src/main/java/ghidra/graph/algo/DepthFirstSorter.java