presto-main/src/main/java/io/prestosql/sql/planner/planprinter/PlanPrinter.java/PlanPrinter/visitSample
class PlanPrinter:        @Override
        public Void visitSample(SampleNode node, Void context)
        {
            addNode(node, "Sample", format("[%s: %s]", node.getSampleType(), node.getSampleRatio()));

            return processChildren(node, context);
        }