presto-main/src/main/java/io/prestosql/util/GraphvizPrinter.java/GraphvizPrinter/visitApply
class GraphvizPrinter:        @Override
        public Void visitApply(ApplyNode node, Void context)
        {
            String parameters = Joiner.on(",").join(node.getCorrelation());
            printNode(node, "Apply", parameters, NODE_COLORS.get(NodeType.JOIN));

            node.getInput().accept(this, context);
            node.getSubquery().accept(this, context);

            return null;
        }