Tuple tuple;
try
{
mOutput.write(ControlBlock.LIST_BEGIN);
List columns = new ArrayList();
ColumnMetadata col0 = new SimpleColumnMetadata("groupID", TupleTypes._STRING, 0, 0, 0);
columns.add(col0);
ColumnMetadata col1 = new SimpleColumnMetadata("groupID", TupleTypes._OBJECT, 0, 0, 0);
columns.add(col1);
TupleMetadata metadata = new SimpleTupleMetadata(columns);
MetadataWrapper wrapper = new MetadataWrapper(metadata);
mOutput.write(wrapper);
while ((tuple = Next(tuples)) != null)