presto-orc/src/main/java/io/prestosql/orc/RowGroup.java/RowGroup/toString
class RowGroup:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("groupId", groupId)
                .add("rowOffset", rowOffset)
                .add("rowCount", rowCount)
                .add("minAverageRowBytes", minAverageRowBytes)
                .add("streamSources", streamSources)
                .toString();
    }