presto-main/src/main/java/io/prestosql/sql/planner/planprinter/IoPlanPrinter.java/FormattedMarker/toString
class FormattedMarker:        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("value", value)
                    .add("bound", bound)
                    .toString();
        }