code: private static Schema singleFieldToTupleSchema(String fieldName, Field field) throws FrontendException {
      switch (field.getType()) {
        case TType.STRUCT:
          return wrapInTupleIfPig9(toSchema(field.gettStructDescriptor()));
        case TType.LIST:
        case TType.SET:
        case TType.MAP:
          return wrapInTupleIfPig9(new Schema(singleFieldToFieldSchema(fieldName, field)));
        default:
          return wrapInTupleIfPig9(new Schema(new FieldSchema(fieldName, null, getPigDataType(field))));
      }
    }
docs: Returns a schema with single tuple (for Pig bags).