presto-main/src/main/java/io/prestosql/sql/planner/optimizations/PreferredProperties.java/PreferredProperties/toString
class PreferredProperties:        @Override
        public String toString()
        {
            return toStringHelper(this)
                    .add("distributed", distributed)
                    .add("partitioningProperties", partitioningProperties)
                    .toString();
        }