presto-main/src/main/java/io/prestosql/operator/PagesIndex.java/PagesIndex/toString
class PagesIndex:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("positionCount", positionCount)
                .add("types", types)
                .add("estimatedSize", estimatedSize)
                .toString();
    }