transform method

@override String transform()

Implementation

@override
String transform() {
  //space is mandatory
  final filteredOperands = operands
      .map((e) => e.transform())
      .where((element) => element.isNotEmpty);
  if (filteredOperands.isEmpty) {
    return '';
  } else if (filteredOperands.length == 1) {
    return filteredOperands.first;
  } else {
    return filteredOperands.map((e) => '($e)').join(" AND ");
  }
}