presto-thrift-api/src/main/java/io/prestosql/plugin/thrift/api/PrestoThriftNullableColumnSet.java/PrestoThriftNullableColumnSet/getColumns
class PrestoThriftNullableColumnSet:    @Nullable
    @ThriftField(value = 1, requiredness = OPTIONAL)
    public Set<String> getColumns()
    {
        return columns;
    }