presto-thrift-api/src/main/java/io/prestosql/plugin/thrift/api/PrestoThriftDomain.java/PrestoThriftDomain/toString
class PrestoThriftDomain:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("valueSet", valueSet)
                .add("nullAllowed", nullAllowed)
                .toString();
    }