code: public static <N, E> void write(Graph<N, E> graph, Appendable a) throws IOException {
          writeRaw(graph, a, toDOTVisualizationHelper(graph.getVisualizationHelper()));
      }
docs: Renders a {@link Graph} in the GraphVIZ DOT format.
  
  @param graph
  the graph to render
  @param a
  the appendable to write to.
  
  @throws IOException
  if writing to {@code a} fails.