presto-main/src/main/java/io/prestosql/sql/planner/optimizations/StreamPreferredProperties.java/StreamPreferredProperties/toString
class StreamPreferredProperties:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("distribution", distribution.orElse(null))
                .add("partitioningColumns", partitioningColumns.orElse(null))
                .omitNullValues()
                .toString();
    }